diff --git a/src/wp-includes/feed-atom-comments.php b/src/wp-includes/feed-atom-comments.php
index 1de77e3917..dc8060395c 100644
--- a/src/wp-includes/feed-atom-comments.php
+++ b/src/wp-includes/feed-atom-comments.php
@@ -30,13 +30,13 @@ do_action( 'rss_tag_pre', 'atom-comments' );
 	<title type="text">
 	<?php
 	if ( is_singular() ) {
-		/* translators: Comments feed title. %s: Post title. */
+		/* translators: Comments feed title. %s: Post title. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 		printf( ent2ncr( __( 'Comments on %s' ) ), get_the_title_rss() );
 	} elseif ( is_search() ) {
-		/* translators: Comments feed title. 1: Site title, 2: Search query. */
+		/* translators: Comments feed title. 1: Site title, 2: Search query. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 		printf( ent2ncr( __( 'Comments for %1$s searching on %2$s' ) ), get_bloginfo_rss( 'name' ), get_search_query() );
 	} else {
-		/* translators: Comments feed title. %s: Site title. */
+		/* translators: Comments feed title. %s: Site title. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 		printf( ent2ncr( __( 'Comments for %s' ) ), get_wp_title_rss() );
 	}
 	?>
@@ -82,10 +82,10 @@ while ( have_comments() ) :
 			$title = get_the_title( $comment_post->ID );
 			/** This filter is documented in wp-includes/feed.php */
 			$title = apply_filters( 'the_title_rss', $title );
-			/* translators: Individual comment title. 1: Post title, 2: Comment author name. */
+			/* translators: Individual comment title. 1: Post title, 2: Comment author name. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 			printf( ent2ncr( __( 'Comment on %1$s by %2$s' ) ), $title, get_comment_author_rss() );
 		} else {
-			/* translators: Comment author title. %s: Comment author name. */
+			/* translators: Comment author title. %s: Comment author name. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 			printf( ent2ncr( __( 'By: %s' ) ), get_comment_author_rss() );
 		}
 		?>
diff --git a/src/wp-includes/feed-rss2-comments.php b/src/wp-includes/feed-rss2-comments.php
index 85a4079fa0..d36d5a8e30 100644
--- a/src/wp-includes/feed-rss2-comments.php
+++ b/src/wp-includes/feed-rss2-comments.php
@@ -35,13 +35,13 @@ do_action( 'rss_tag_pre', 'rss2-comments' );
 	<title>
 	<?php
 	if ( is_singular() ) {
-		/* translators: Comments feed title. %s: Post title. */
+		/* translators: Comments feed title. %s: Post title. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 		printf( ent2ncr( __( 'Comments on: %s' ) ), get_the_title_rss() );
 	} elseif ( is_search() ) {
-		/* translators: Comments feed title. 1: Site title, 2: Search query. */
+		/* translators: Comments feed title. 1: Site title, 2: Search query. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 		printf( ent2ncr( __( 'Comments for %1$s searching on %2$s' ) ), get_bloginfo_rss( 'name' ), get_search_query() );
 	} else {
-		/* translators: Comments feed title. %s: Site title. */
+		/* translators: Comments feed title. %s: Site title. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 		printf( ent2ncr( __( 'Comments for %s' ) ), get_wp_title_rss() );
 	}
 	?>
@@ -85,10 +85,10 @@ do_action( 'rss_tag_pre', 'rss2-comments' );
 			$title = get_the_title( $comment_post->ID );
 			/** This filter is documented in wp-includes/feed.php */
 			$title = apply_filters( 'the_title_rss', $title );
-			/* translators: Individual comment title. 1: Post title, 2: Comment author name. */
+			/* translators: Individual comment title. 1: Post title, 2: Comment author name. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 			printf( ent2ncr( __( 'Comment on %1$s by %2$s' ) ), $title, get_comment_author_rss() );
 		} else {
-			/* translators: Comment author title. %s: Comment author name. */
+			/* translators: Comment author title. %s: Comment author name. Do not use HTML entities (&nbsp;, etc.) - used in RSS feeds. */
 			printf( ent2ncr( __( 'By: %s' ) ), get_comment_author_rss() );
 		}
 		?>
diff --git a/src/wp-includes/pluggable.php b/src/wp-includes/pluggable.php
index 1dbac5e1d7..9567aa3640 100644
--- a/src/wp-includes/pluggable.php
+++ b/src/wp-includes/pluggable.php
@@ -1792,7 +1792,7 @@ if ( ! function_exists( 'wp_notify_postauthor' ) ) :
 					$notify_message = sprintf( __( 'New trackback on your post "%s"' ), $post->post_title ) . "\r\n";
 					/* translators: 1: Trackback/pingback website name, 2: Website IP address, 3: Website hostname. */
 					$notify_message .= sprintf( __( 'Website: %1$s (IP address: %2$s, %3$s)' ), $comment->comment_author, $comment->comment_author_IP, $comment_author_domain ) . "\r\n";
-					/* translators: %s: Trackback/pingback/comment author URL. */
+					/* translators: %s: Trackback/pingback/comment author URL. Do not use HTML entities (&nbsp;, etc.) - used in emails. */
 					$notify_message .= sprintf( __( 'URL: %s' ), $comment->comment_author_url ) . "\r\n";
 					/* translators: %s: Comment text. */
 					$notify_message .= sprintf( __( 'Comment: %s' ), "\r\n" . $comment_content ) . "\r\n\r\n";
@@ -1806,7 +1806,7 @@ if ( ! function_exists( 'wp_notify_postauthor' ) ) :
 					$notify_message = sprintf( __( 'New pingback on your post "%s"' ), $post->post_title ) . "\r\n";
 					/* translators: 1: Trackback/pingback website name, 2: Website IP address, 3: Website hostname. */
 					$notify_message .= sprintf( __( 'Website: %1$s (IP address: %2$s, %3$s)' ), $comment->comment_author, $comment->comment_author_IP, $comment_author_domain ) . "\r\n";
-					/* translators: %s: Trackback/pingback/comment author URL. */
+					/* translators: %s: Trackback/pingback/comment author URL. Do not use HTML entities (&nbsp;, etc.) - used in emails. */
 					$notify_message .= sprintf( __( 'URL: %s' ), $comment->comment_author_url ) . "\r\n";
 					/* translators: %s: Comment text. */
 					$notify_message .= sprintf( __( 'Comment: %s' ), "\r\n" . $comment_content ) . "\r\n\r\n";