Don’t escape the html comment.

Author: joeyblake

core/Walker/Nav_Menu_Item_Edit_Walker.php

@@ -26,7 +26,7 @@ public function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0
 		// Generates the HTML
 		ob_start();
 		do_action( 'carbon_fields_print_nav_menu_item_container_fields', $item, $output, $depth, $args, $id );
-		echo esc_html( $flag );
+		echo $flag; // XSS ok. Just an html comment.
 		$fields = ob_get_clean();
 
 		// List of possible insertion markers, this may vary between WP Core versions