Index: src/wp-includes/class-wp-editor.php
===================================================================
--- src/wp-includes/class-wp-editor.php	(revision 45589)
+++ src/wp-includes/class-wp-editor.php	(working copy)
@@ -538,18 +538,24 @@
 					$settings['wpeditimage_disable_captions'] = true;
 				}
 
-				$mce_css       = $settings['content_css'];
-				$editor_styles = get_editor_stylesheets();
+				$mce_css = $settings['content_css'];
 
-				if ( ! empty( $editor_styles ) ) {
-					// Force urlencoding of commas.
-					foreach ( $editor_styles as $key => $url ) {
-						if ( strpos( $url, ',' ) !== false ) {
-							$editor_styles[ $key ] = str_replace( ',', '%2C', $url );
+				// The `editor-style.css` added by the theme is generally intended for the editor instance on the Edit Post screen.
+				// Plugins that use wp_editor() on the front-end can decide whether to add the theme stylesheet
+				// by using `get_editor_stylesheets()` and the `mce_css` or `tiny_mce_before_init` filters, see below.
+				if ( is_admin() ) {
+					$editor_styles = get_editor_stylesheets();
+
+					if ( ! empty( $editor_styles ) ) {
+						// Force urlencoding of commas.
+						foreach ( $editor_styles as $key => $url ) {
+							if ( strpos( $url, ',' ) !== false ) {
+								$editor_styles[ $key ] = str_replace( ',', '%2C', $url );
+							}
 						}
+
+						$mce_css .= ',' . implode( ',', $editor_styles );
 					}
-
-					$mce_css .= ',' . implode( ',', $editor_styles );
 				}
 
 				/**
Index: src/wp-includes/theme.php
===================================================================
--- src/wp-includes/theme.php	(revision 45589)
+++ src/wp-includes/theme.php	(working copy)
@@ -1914,15 +1914,13 @@
  *                                 Defaults to 'editor-style.css'
  */
 function add_editor_style( $stylesheet = 'editor-style.css' ) {
+	global $editor_styles;
+
 	add_theme_support( 'editor-style' );
 
-	if ( ! is_admin() ) {
-		return;
-	}
-
-	global $editor_styles;
 	$editor_styles = (array) $editor_styles;
 	$stylesheet    = (array) $stylesheet;
+
 	if ( is_rtl() ) {
 		$rtl_stylesheet = str_replace( '.css', '-rtl.css', $stylesheet[0] );
 		$stylesheet[]   = $rtl_stylesheet;