Ticket #47642: 47642.diff

src/wp-includes/class-wp-query.php

@@ -2325 +2325 @@
                 } elseif ( 'none' === $q['orderby'] ) {
                         $orderby = '';
                 } else {
+                        // https://core.trac.wordpress.org/ticket/47642
+                        if ( 'comment_count' === $q['orderby'] ) {
+                                $q['orderby'] = 'comment_count ID';
+                        }
+
                         $orderby_array = array();
                         if ( is_array( $q['orderby'] ) ) {
                                 foreach ( $q['orderby'] as $_orderby => $order ) {