diff --git a/src/wp-includes/customize/class-wp-customize-custom-css-setting.php b/src/wp-includes/customize/class-wp-customize-custom-css-setting.php
index 3189ae9262..ad0c70caa1 100644
--- a/src/wp-includes/customize/class-wp-customize-custom-css-setting.php
+++ b/src/wp-includes/customize/class-wp-customize-custom-css-setting.php
@@ -175,25 +175,47 @@ final class WP_Customize_Custom_CSS_Setting extends WP_Customize_Setting {
 
 		// Make sure that there is a closing brace for each opening brace.
 		if ( ! $this->validate_balanced_characters( '{', '}', $css ) ) {
-			$validity->add( 'imbalanced_curly_brackets', __( 'Your curly brackets <code>{}</code> are imbalanced. Make sure there is a closing <code>}</code> for every opening <code>{</code>.' ) );
+			$validity->add( 'imbalanced_curly_brackets', sprintf(
+				/* translators: 1: {}, 2: }, 3: { */
+				__( 'Your curly brackets %1$s are imbalanced. Make sure there is a closing %2$s for every opening %3$s.' ),
+				'<code>{}</code>',
+				'<code>}</code>',
+				'<code>{</code>'
+			) );
 			$imbalanced = true;
 		}
 
 		// Ensure brackets are balanced.
 		if ( ! $this->validate_balanced_characters( '[', ']', $css ) ) {
-			$validity->add( 'imbalanced_braces', __( 'Your brackets <code>[]</code> are imbalanced. Make sure there is a closing <code>]</code> for every opening <code>[</code>.' ) );
+			$validity->add( 'imbalanced_braces', sprintf(
+				/* translators: 1: [], 2: ], 3: [ */
+				__( 'Your brackets %1$s are imbalanced. Make sure there is a closing %2$s for every opening %3$s.' ),
+				'<code>[]</code>',
+				'<code>]</code>',
+				'<code>[</code>'
+			) );
 			$imbalanced = true;
 		}
 
 		// Ensure parentheses are balanced.
 		if ( ! $this->validate_balanced_characters( '(', ')', $css ) ) {
-			$validity->add( 'imbalanced_parentheses', __( 'Your parentheses <code>()</code> are imbalanced. Make sure there is a closing <code>)</code> for every opening <code>(</code>.' ) );
+			$validity->add( 'imbalanced_parentheses', sprintf(
+				/* translators: 1: (), 2: ), 3: ( */
+				__( 'Your parentheses %1$s are imbalanced. Make sure there is a closing %2$s for every opening %3$s.' ),
+				'<code>()</code>',
+				'<code>)</code>',
+				'<code>(</code>'
+			) );
 			$imbalanced = true;
 		}
 
 		// Ensure double quotes are equal.
 		if ( ! $this->validate_equal_characters( '"', $css ) ) {
-			$validity->add( 'unequal_double_quotes', __( 'Your double quotes <code>"</code> are uneven. Make sure there is a closing <code>"</code> for every opening <code>"</code>.' ) );
+			$validity->add( 'unequal_double_quotes', sprintf(
+				/* translators: %s: " */
+				__( 'Your double quotes %s are uneven. Make sure there is a closing %s for every opening %s.' ),
+				'<code>"</code>'
+			) );
 			$imbalanced = true;
 		}
 
@@ -209,14 +231,32 @@ final class WP_Customize_Custom_CSS_Setting extends WP_Customize_Setting {
 		 */
 		$unclosed_comment_count = $this->validate_count_unclosed_comments( $css );
 		if ( 0 < $unclosed_comment_count ) {
-			$validity->add( 'unclosed_comment', sprintf( _n( 'There is %s unclosed code comment. Close each comment with <code>*/</code>.', 'There are %s unclosed code comments. Close each comment with <code>*/</code>.', $unclosed_comment_count ), $unclosed_comment_count ) );
+			$validity->add( 'unclosed_comment', sprintf(
+				/* translators: 1: number of unclosed comments, 2: *​/ */
+				_n(
+					'There is %1$s unclosed code comment. Close each comment with %2$s.',
+					'There are %1$s unclosed code comments. Close each comment with %2$s.',
+					$unclosed_comment_count
+				),
+				$unclosed_comment_count,
+				'<code>*/</code>'
+			) );
 			$imbalanced = true;
 		} elseif ( ! $this->validate_balanced_characters( '/*', '*/', $css ) ) {
-			$validity->add( 'imbalanced_comments', __( 'There is an extra <code>*/</code>, indicating an end to a comment.  Be sure that there is an opening <code>/*</code> for every closing <code>*/</code>.' ) );
+			$validity->add( 'imbalanced_comments', sprintf(
+				/* translators: 1: *​/, 2: /​* */
+				__( 'There is an extra %1$s, indicating an end to a comment. Be sure that there is an opening %2$s for every closing %1$s.' ),
+				'<code>*/</code>',
+				'<code>/*</code>'
+			) );
 			$imbalanced = true;
 		}
 		if ( $imbalanced && $this->is_possible_content_error( $css ) ) {
-			$validity->add( 'possible_false_positive', __( 'Imbalanced/unclosed character errors can be caused by <code>content: "";</code> declarations. You may need to remove this or add it to a custom CSS file.' ) );
+			$validity->add( 'possible_false_positive', sprintf(
+				/* translators: %s: content: ""; */
+				__( 'Imbalanced/unclosed character errors can be caused by %s declarations. You may need to remove this or add it to a custom CSS file.' ),
+				'<code>content: "";</code>'
+			) );
 		}
 
 		if ( empty( $validity->errors ) ) {