Index: src/wp-admin/includes/post.php
===================================================================
--- src/wp-admin/includes/post.php	(revision 29719)
+++ src/wp-admin/includes/post.php	(working copy)
@@ -1207,7 +1207,7 @@
 	} else {
 		if ( function_exists( 'mb_strlen' ) && mb_strlen( $post_name ) > 30 ) {
 			$post_name_abridged = mb_substr( $post_name, 0, 14 ) . '…' . mb_substr( $post_name, -14 );
-		} elseif ( strlen( $post_name ) > 30 ) {
+		} elseif ( ! seems_utf8( $post_name ) && strlen( $post_name ) > 30 ) {
 			$post_name_abridged = substr( $post_name, 0, 14 ) . '…' . substr( $post_name, -14 );
 		} else {
 			$post_name_abridged = $post_name;
Index: tests/phpunit/tests/post.php
===================================================================
--- tests/phpunit/tests/post.php	(revision 29719)
+++ tests/phpunit/tests/post.php	(working copy)
@@ -499,6 +499,53 @@
 	}
 
 	/**
+	 * @ticket 29573
+	 */
+	function test_get_sample_permalink_html_with_non_latin_slugs() {
+		$inputs = array(
+			'Αρνάκι άσπρο και παχύ της μάνας του καμάρι, και άλλα τραγούδια',
+			'Предлагаем супер металлообрабатывающее оборудование',
+			'בניית אתרי וורדפרס',
+		);
+
+		$outputs_mbstring_enabled = array(
+			'αρνάκι-άσπρο-κ…-μάνας-του-καμ',
+			'предлагаем-суп…ллообрабатываю',
+			'בניית-אתרי-וורדפרס',
+		);
+
+		$outputs_mbstring_disabled = array(
+			'αρνάκι-άσπρο-και-παχύ-της-μάνας-του-καμ',
+			'предлагаем-супер-металлообрабатываю',
+			'בניית-אתרי-וורדפרס',
+		);
+
+		$old_permastruct = get_option( 'permalink_structure' );
+		update_option( 'permalink_structure', '/%postname%/' );
+
+		foreach ( $inputs as $k => $post_title ) {
+			$post = array(
+				'post_author' => $this->author_id,
+				'post_status' => 'publish',
+				'post_content' => rand_str(),
+				'post_title' => $post_title,
+			);
+
+			$id = $this->post_ids[] = wp_insert_post( $post );
+			$sample_permalink_html = get_sample_permalink_html( $id );
+			preg_match( '#<span id="editable-post-name".*?>(.+?)</span>#', $sample_permalink_html, $matches );
+
+			if ( function_exists( 'mb_strlen' ) ) {
+				$this->assertEquals( $outputs_mbstring_enabled[ $k ], $matches[1] );
+			} else {
+				$this->assertEquals( $outputs_mbstring_disabled[ $k ], $matches[1] );
+			}
+		}
+
+		update_option( 'permalink_structure', $old_permastruct );
+	}
+
+	/**
 	 * @ticket 15665
 	 */
 	function test_get_page_by_path_priority() {