Index: src/wp-admin/includes/class-wp-media-list-table.php
===================================================================
--- src/wp-admin/includes/class-wp-media-list-table.php	(revision 52573)
+++ src/wp-admin/includes/class-wp-media-list-table.php	(working copy)
@@ -633,8 +633,7 @@
 						esc_html( sanitize_term_field( 'name', $t->name, $t->term_id, $taxonomy, 'display' ) )
 					);
 				}
-				/* translators: Used between list items, there is a space after the comma. */
-				echo implode( __( ', ' ), $out );
+				echo implode( wp_get_list_item_separator(), $out );
 			} else {
 				echo '<span aria-hidden="true">&#8212;</span><span class="screen-reader-text">' . get_taxonomy( $taxonomy )->labels->no_terms . '</span>';
 			}
Index: src/wp-admin/includes/class-wp-posts-list-table.php
===================================================================
--- src/wp-admin/includes/class-wp-posts-list-table.php	(revision 52573)
+++ src/wp-admin/includes/class-wp-posts-list-table.php	(working copy)
@@ -1294,8 +1294,7 @@
 				 */
 				$term_links = apply_filters( 'post_column_taxonomy_links', $term_links, $taxonomy, $terms );
 
-				/* translators: Used between list items, there is a space after the comma. */
-				echo implode( __( ', ' ), $term_links );
+				echo implode( wp_get_list_item_separator(), $term_links );
 			} else {
 				echo '<span aria-hidden="true">&#8212;</span><span class="screen-reader-text">' . $taxonomy_object->labels->no_terms . '</span>';
 			}
Index: src/wp-content/themes/twentyeleven/content-featured.php
===================================================================
--- src/wp-content/themes/twentyeleven/content-featured.php	(revision 52573)
+++ src/wp-content/themes/twentyeleven/content-featured.php	(working copy)
@@ -32,8 +32,7 @@
 
 	<footer class="entry-meta">
 		<?php
-		/* translators: Used between list items, there is a space after the comma. */
-		$tags_list = get_the_tag_list( '', __( ', ', 'twentyeleven' ) );
+		$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 
 		if ( $tags_list && ! is_wp_error( $tags_list ) ) {
 			/* translators: 1: Category list, 2: Tag list, 3: Post permalink, 4: Post title. */
@@ -45,8 +44,7 @@
 
 		printf(
 			$utility_text,
-			/* translators: Used between list items, there is a space after the comma. */
-			get_the_category_list( __( ', ', 'twentyeleven' ) ),
+			get_the_category_list( wp_get_list_item_separator() ),
 			$tags_list,
 			esc_url( get_permalink() ),
 			the_title_attribute( 'echo=0' )
Index: src/wp-content/themes/twentyeleven/content-gallery.php
===================================================================
--- src/wp-content/themes/twentyeleven/content-gallery.php	(revision 52573)
+++ src/wp-content/themes/twentyeleven/content-gallery.php	(working copy)
@@ -72,8 +72,7 @@
 		<?php $show_sep = false; ?>
 
 		<?php
-		/* translators: Used between list items, there is a space after the comma. */
-		$categories_list = get_the_category_list( __( ', ', 'twentyeleven' ) );
+		$categories_list = get_the_category_list( wp_get_list_item_separator() );
 
 		if ( $categories_list ) :
 			?>
@@ -87,8 +86,7 @@
 		<?php endif; // End if categories. ?>
 
 		<?php
-		/* translators: Used between list items, there is a space after the comma. */
-		$tags_list = get_the_tag_list( '', __( ', ', 'twentyeleven' ) );
+		$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 
 		if ( $tags_list && ! is_wp_error( $tags_list ) ) :
 			if ( $show_sep ) :
Index: src/wp-content/themes/twentyeleven/content-image.php
===================================================================
--- src/wp-content/themes/twentyeleven/content-image.php	(revision 52573)
+++ src/wp-content/themes/twentyeleven/content-image.php	(working copy)
@@ -55,8 +55,7 @@
 			</div><!-- .entry-meta -->
 			<div class="entry-meta">
 				<?php
-				/* translators: Used between list items, there is a space after the comma. */
-				$categories_list = get_the_category_list( __( ', ', 'twentyeleven' ) );
+				$categories_list = get_the_category_list( wp_get_list_item_separator() );
 
 				if ( $categories_list ) :
 					?>
@@ -69,8 +68,7 @@
 				<?php endif; // End if categories. ?>
 
 				<?php
-				/* translators: Used between list items, there is a space after the comma. */
-				$tags_list = get_the_tag_list( '', __( ', ', 'twentyeleven' ) );
+				$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 
 				if ( $tags_list && ! is_wp_error( $tags_list ) ) :
 					?>
Index: src/wp-content/themes/twentyeleven/content-quote.php
===================================================================
--- src/wp-content/themes/twentyeleven/content-quote.php	(revision 52573)
+++ src/wp-content/themes/twentyeleven/content-quote.php	(working copy)
@@ -48,8 +48,7 @@
 			<?php $show_sep = false; ?>
 
 			<?php
-			/* translators: Used between list items, there is a space after the comma. */
-			$categories_list = get_the_category_list( __( ', ', 'twentyeleven' ) );
+			$categories_list = get_the_category_list( wp_get_list_item_separator() );
 
 			if ( $categories_list ) :
 				?>
@@ -64,7 +63,7 @@
 
 			<?php
 			/* translators: Used between list items, there is a space after the comma. */
-			$tags_list = get_the_tag_list( '', __( ', ', 'twentyeleven' ) );
+			$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 
 			if ( $tags_list && ! is_wp_error( $tags_list ) ) :
 				if ( $show_sep ) :
Index: src/wp-content/themes/twentyeleven/content-single.php
===================================================================
--- src/wp-content/themes/twentyeleven/content-single.php	(revision 52573)
+++ src/wp-content/themes/twentyeleven/content-single.php	(working copy)
@@ -33,11 +33,9 @@
 
 	<footer class="entry-meta">
 		<?php
-		/* translators: Used between list items, there is a space after the comma. */
-		$categories_list = get_the_category_list( __( ', ', 'twentyeleven' ) );
+		$categories_list = get_the_category_list( wp_get_list_item_separator() );
 
-		/* translators: Used between list items, there is a space after the comma. */
-		$tags_list = get_the_tag_list( '', __( ', ', 'twentyeleven' ) );
+		$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 
 		if ( $tags_list && ! is_wp_error( $tags_list ) ) {
 			/* translators: 1: Categories list, 2: Tag list, 3: Permalink, 4: Post title, 5: Author name, 6: Author URL. */
Index: src/wp-content/themes/twentyeleven/content.php
===================================================================
--- src/wp-content/themes/twentyeleven/content.php	(revision 52573)
+++ src/wp-content/themes/twentyeleven/content.php	(working copy)
@@ -55,8 +55,7 @@
 
 			<?php if ( is_object_in_taxonomy( get_post_type(), 'category' ) ) : // Hide category text when not supported. ?>
 				<?php
-				/* translators: Used between list items, there is a space after the comma. */
-				$categories_list = get_the_category_list( __( ', ', 'twentyeleven' ) );
+				$categories_list = get_the_category_list( wp_get_list_item_separator() );
 
 				if ( $categories_list ) :
 					?>
@@ -72,8 +71,7 @@
 
 			<?php if ( is_object_in_taxonomy( get_post_type(), 'post_tag' ) ) : // Hide tag text when not supported. ?>
 				<?php
-				/* translators: Used between list items, there is a space after the comma. */
-				$tags_list = get_the_tag_list( '', __( ', ', 'twentyeleven' ) );
+				$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 
 				if ( $tags_list && ! is_wp_error( $tags_list ) ) :
 					if ( $show_sep ) :
Index: src/wp-content/themes/twentyeleven/functions.php
===================================================================
--- src/wp-content/themes/twentyeleven/functions.php	(revision 52573)
+++ src/wp-content/themes/twentyeleven/functions.php	(working copy)
@@ -929,3 +929,16 @@
 	}
 }
 add_action( 'wp_body_open', 'twentyeleven_skip_link', 5 );
+
+if ( ! function_exists( 'wp_get_list_item_separator' ) ) :
+	/**
+	 * Retrieve the list item separator based on the locale.
+	 *
+	 * Added for backward compatibility to support pre-5.9.0 WordPress versions.
+	 *
+	 * @since 5.9.0
+	 */
+	function wp_get_list_item_separator() {
+		return __( ', ', 'twentyeleven' );
+	}
+endif;
Index: src/wp-content/themes/twentynineteen/functions.php
===================================================================
--- src/wp-content/themes/twentynineteen/functions.php	(revision 52573)
+++ src/wp-content/themes/twentynineteen/functions.php	(working copy)
@@ -182,6 +182,19 @@
 endif;
 add_action( 'after_setup_theme', 'twentynineteen_setup' );
 
+if ( ! function_exists( 'wp_get_list_item_separator' ) ) :
+	/**
+	 * Retrieve the list item separator based on the locale.
+	 *
+	 * Added for backward compatibility to support pre-5.9.0 WordPress versions.
+	 *
+	 * @since 5.9.0
+	 */
+	function wp_get_list_item_separator() {
+		return __( ', ', 'twentyeleven' );
+	}
+endif;
+
 /**
  * Register widget area.
  *
Index: src/wp-content/themes/twentynineteen/inc/template-tags.php
===================================================================
--- src/wp-content/themes/twentynineteen/inc/template-tags.php	(revision 52573)
+++ src/wp-content/themes/twentynineteen/inc/template-tags.php	(working copy)
@@ -82,8 +82,7 @@
 			// Posted on.
 			twentynineteen_posted_on();
 
-			/* translators: Used between list items, there is a space after the comma. */
-			$categories_list = get_the_category_list( __( ', ', 'twentynineteen' ) );
+			$categories_list = get_the_category_list( wp_get_list_item_separator() );
 			if ( $categories_list ) {
 				printf(
 					/* translators: 1: SVG icon. 2: Posted in label, only visible to screen readers. 3: List of categories. */
@@ -94,8 +93,7 @@
 				); // WPCS: XSS OK.
 			}
 
-			/* translators: Used between list items, there is a space after the comma. */
-			$tags_list = get_the_tag_list( '', __( ', ', 'twentynineteen' ) );
+			$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 			if ( $tags_list && ! is_wp_error( $tags_list ) ) {
 				printf(
 					/* translators: 1: SVG icon. 2: Posted in label, only visible to screen readers. 3: List of tags. */
Index: src/wp-content/themes/twentyseventeen/functions.php
===================================================================
--- src/wp-content/themes/twentyseventeen/functions.php	(revision 52573)
+++ src/wp-content/themes/twentyseventeen/functions.php	(working copy)
@@ -676,3 +676,16 @@
  * Block Patterns.
  */
 require get_template_directory() . '/inc/block-patterns.php';
+
+if ( ! function_exists( 'wp_get_list_item_separator' ) ) :
+	/**
+	 * Retrieve the list item separator based on the locale.
+	 *
+	 * Added for backward compatibility to support pre-5.9.0 WordPress versions.
+	 *
+	 * @since 5.9.0
+	 */
+	function wp_get_list_item_separator() {
+		return __( ', ', 'twentyseventeen' );
+	}
+endif;
Index: src/wp-content/themes/twentyseventeen/inc/template-tags.php
===================================================================
--- src/wp-content/themes/twentyseventeen/inc/template-tags.php	(revision 52573)
+++ src/wp-content/themes/twentyseventeen/inc/template-tags.php	(working copy)
@@ -62,8 +62,7 @@
 	 */
 	function twentyseventeen_entry_footer() {
 
-		/* translators: Used between list items, there is a space after the comma. */
-		$separate_meta = __( ', ', 'twentyseventeen' );
+		$separate_meta = wp_get_list_item_separator();
 
 		// Get Categories for posts.
 		$categories_list = get_the_category_list( $separate_meta );
Index: src/wp-content/themes/twentythirteen/functions.php
===================================================================
--- src/wp-content/themes/twentythirteen/functions.php	(revision 52573)
+++ src/wp-content/themes/twentythirteen/functions.php	(working copy)
@@ -411,6 +411,19 @@
 }
 add_action( 'widgets_init', 'twentythirteen_widgets_init' );
 
+if ( ! function_exists( 'wp_get_list_item_separator' ) ) :
+	/**
+	 * Retrieve the list item separator based on the locale.
+	 *
+	 * Added for backward compatibility to support pre-5.9.0 WordPress versions.
+	 *
+	 * @since 5.9.0
+	 */
+	function wp_get_list_item_separator() {
+		return __( ', ', 'twentythirteen' );
+	}
+endif;
+
 if ( ! function_exists( 'twentythirteen_paging_nav' ) ) :
 	/**
 	 * Display navigation to next/previous set of posts when applicable.
@@ -490,14 +503,12 @@
 			twentythirteen_entry_date();
 		}
 
-		/* translators: Used between list items, there is a space after the comma. */
-		$categories_list = get_the_category_list( __( ', ', 'twentythirteen' ) );
+		$categories_list = get_the_category_list( wp_get_list_item_separator() );
 		if ( $categories_list ) {
 			echo '<span class="categories-links">' . $categories_list . '</span>';
 		}
 
-		/* translators: Used between list items, there is a space after the comma. */
-		$tags_list = get_the_tag_list( '', __( ', ', 'twentythirteen' ) );
+		$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 		if ( $tags_list && ! is_wp_error( $tags_list ) ) {
 			echo '<span class="tags-links">' . $tags_list . '</span>';
 		}
Index: src/wp-content/themes/twentytwelve/functions.php
===================================================================
--- src/wp-content/themes/twentytwelve/functions.php	(revision 52573)
+++ src/wp-content/themes/twentytwelve/functions.php	(working copy)
@@ -384,6 +384,19 @@
 }
 add_action( 'widgets_init', 'twentytwelve_widgets_init' );
 
+if ( ! function_exists( 'wp_get_list_item_separator' ) ) :
+	/**
+	 * Retrieve the list item separator based on the locale.
+	 *
+	 * Added for backward compatibility to support pre-5.9.0 WordPress versions.
+	 *
+	 * @since 5.9.0
+	 */
+	function wp_get_list_item_separator() {
+		return __( ', ', 'twentytwelve' );
+	}
+endif;
+
 if ( ! function_exists( 'twentytwelve_content_nav' ) ) :
 	/**
 	 * Displays navigation to next/previous pages when applicable.
@@ -502,11 +515,9 @@
 	 * @since Twenty Twelve 1.0
 	 */
 	function twentytwelve_entry_meta() {
-		/* translators: Used between list items, there is a space after the comma. */
-		$categories_list = get_the_category_list( __( ', ', 'twentytwelve' ) );
+		$categories_list = get_the_category_list( wp_get_list_item_separator() );
 
-		/* translators: Used between list items, there is a space after the comma. */
-		$tags_list = get_the_tag_list( '', __( ', ', 'twentytwelve' ) );
+		$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 
 		$date = sprintf(
 			'<a href="%1$s" title="%2$s" rel="bookmark"><time class="entry-date" datetime="%3$s">%4$s</time></a>',
Index: src/wp-content/themes/twentytwentyone/functions.php
===================================================================
--- src/wp-content/themes/twentytwentyone/functions.php	(revision 52573)
+++ src/wp-content/themes/twentytwentyone/functions.php	(working copy)
@@ -640,3 +640,16 @@
 	<?php
 }
 add_action( 'wp_footer', 'twentytwentyone_add_ie_class' );
+
+if ( ! function_exists( 'wp_get_list_item_separator' ) ) :
+	/**
+	 * Retrieve the list item separator based on the locale.
+	 *
+	 * Added for backward compatibility to support pre-5.9.0 WordPress versions.
+	 *
+	 * @since 5.9.0
+	 */
+	function wp_get_list_item_separator() {
+		return __( ', ', 'twentytwentyone' );
+	}
+endif;
Index: src/wp-content/themes/twentytwentyone/inc/template-tags.php
===================================================================
--- src/wp-content/themes/twentytwentyone/inc/template-tags.php	(revision 52573)
+++ src/wp-content/themes/twentytwentyone/inc/template-tags.php	(working copy)
@@ -100,8 +100,7 @@
 
 				echo '<div class="post-taxonomies">';
 
-				/* translators: Used between list items, there is a space after the comma. */
-				$categories_list = get_the_category_list( __( ', ', 'twentytwentyone' ) );
+				$categories_list = get_the_category_list( wp_get_list_item_separator() );
 				if ( $categories_list ) {
 					printf(
 						/* translators: %s: List of categories. */
@@ -110,8 +109,7 @@
 					);
 				}
 
-				/* translators: Used between list items, there is a space after the comma. */
-				$tags_list = get_the_tag_list( '', __( ', ', 'twentytwentyone' ) );
+				$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 				if ( $tags_list ) {
 					printf(
 						/* translators: %s: List of tags. */
@@ -144,8 +142,7 @@
 
 				echo '<div class="post-taxonomies">';
 
-				/* translators: Used between list items, there is a space after the comma. */
-				$categories_list = get_the_category_list( __( ', ', 'twentytwentyone' ) );
+				$categories_list = get_the_category_list( wp_get_list_item_separator() );
 				if ( $categories_list ) {
 					printf(
 						/* translators: %s: List of categories. */
@@ -154,8 +151,7 @@
 					);
 				}
 
-				/* translators: Used between list items, there is a space after the comma. */
-				$tags_list = get_the_tag_list( '', __( ', ', 'twentytwentyone' ) );
+				$tags_list = get_the_tag_list( '', wp_get_list_item_separator() );
 				if ( $tags_list ) {
 					printf(
 						/* translators: %s: List of tags. */
Index: src/wp-includes/class-wp-locale.php
===================================================================
--- src/wp-includes/class-wp-locale.php	(revision 52573)
+++ src/wp-includes/class-wp-locale.php	(working copy)
@@ -96,6 +96,14 @@
 	public $number_format;
 
 	/**
+	 * The separator string used for localizing list item separator.
+	 *
+	 * @since 5.9.0
+	 * @var string
+	 */
+	public $list_item_separator;
+
+	/**
 	 * Constructor which calls helper methods to set up object variables.
 	 *
 	 * @since 2.1.0
@@ -209,6 +217,9 @@
 
 		$this->number_format['decimal_point'] = ( 'number_format_decimal_point' === $decimal_point ) ? '.' : $decimal_point;
 
+		/* translators: used between list items, there is a space after the comma */
+		$this->list_item_separator = __( ', ' );
+
 		// Set text direction.
 		if ( isset( $GLOBALS['text_direction'] ) ) {
 			$this->text_direction = $GLOBALS['text_direction'];
@@ -366,4 +377,15 @@
 		/* translators: Localized date and time format, see https://www.php.net/manual/datetime.format.php */
 		__( 'F j, Y g:i a' );
 	}
+
+	/**
+	 * Retrieve the localized list item separator.
+	 *
+	 * @since 5.9.0
+	 *
+	 * @return string Localized list item separator.
+	 */
+	public function get_list_item_separator() {
+		return $this->list_item_separator;
+	}
 }
Index: src/wp-includes/class-wp-theme.php
===================================================================
--- src/wp-includes/class-wp-theme.php	(revision 52573)
+++ src/wp-includes/class-wp-theme.php	(working copy)
@@ -924,8 +924,7 @@
 			case 'Tags':
 				static $comma = null;
 				if ( ! isset( $comma ) ) {
-					/* translators: Used between list items, there is a space after the comma. */
-					$comma = __( ', ' );
+					$comma = wp_get_list_item_separator();
 				}
 				$value = implode( $comma, $value );
 				break;
Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 52573)
+++ src/wp-includes/functions.php	(working copy)
@@ -8376,3 +8376,17 @@
 function wp_fuzzy_number_match( $expected, $actual, $precision = 1 ) {
 	return abs( (float) $expected - (float) $actual ) <= $precision;
 }
+
+/**
+ * Retrieve the list item separator based on the locale.
+ *
+ * @since 5.9.0
+ *
+ * @global WP_Locale $wp_locale WordPress date and time locale object.
+ *
+ * @return string Locale specific list item separator.
+ */
+function wp_get_list_item_separator() {
+	global $wp_locale;
+	return $wp_locale->get_list_item_separator();
+}