Add this code to your theme’s functions.php file:

add_action( 'wp_insert_comment', 'wc_auto_approve_parent_review_on_admin_reply', 99, 2 );

function wc_auto_approve_parent_review_on_admin_reply( $comment_id, $comment_object ) {
    // Ensure it's a reply (has a parent comment)
    if ( $comment_object->comment_parent > 0 ) {

        // Check if the user submitting the reply has moderation capabilities
        if ( current_user_can( 'moderate_comments' ) ) {

            // Get the parent comment object
            $parent_comment = get_comment( $comment_object->comment_parent );

            // Proceed only if parent comment exists
            if ( $parent_comment ) {
                // Check if the parent comment is linked to a 'product' post type
                $parent_post_type = get_post_type( $parent_comment->comment_post_ID );

                // Check if parent is a product review AND is currently unapproved ('0')
                if ( $parent_post_type === 'product' && $parent_comment->comment_approved === '0' ) {

                    // Approve the parent comment
                    // Use wp_set_comment_status() for better compatibility/hooks
                    wp_set_comment_status( $parent_comment->comment_ID, 'approve' );

                    // Optional: Clean comment cache for the parent post if needed,
                    // though status change usually handles this.
                    // clean_comment_cache( $parent_comment->comment_ID );
                }
            }
        }
    }
}

Create a file named admin-comment-reply.js in your theme directory (theme/js/). and Paste the following jQuery code into that file:

jQuery(document).ready(function($) {
    // Listen for successful AJAX requests within the document
    $(document).ajaxSuccess(function(event, xhr, settings) {
        
        if ( settings.data && typeof settings.data === 'string' && settings.data.includes('action=replyto-comment') ) {

            
            const requestData = new URLSearchParams(settings.data);
            const parentCommentId = requestData.get('comment_ID'); 

            if ( parentCommentId ) {
                // Find the parent comment's row element in the comment list table
                // The row usually has an ID like 'comment-{id}'
                const $parentCommentRow = $('#comment-' + parentCommentId);

                if ($parentCommentRow.length) {
                    
                    setTimeout(function() {
                        // Check if the row still has the 'unapproved' class
                        if ( $parentCommentRow.hasClass('unapproved') ) {
                            console.log('Admin reply successful, removing unapproved style from parent comment #' + parentCommentId); // For debugging
                            
                            $parentCommentRow.removeClass('unapproved').css('backgroundColor', '');
                        }
                    }, 150); // 150ms delay, adjust if needed
                }
            } else {
                console.log('Could not find parent comment ID in replyto-comment AJAX data.'); // For debugging
            }
        }
    });
});

Enqueue the JS file for the Admin Area:

add_action( 'admin_enqueue_scripts', 'wc_enqueue_admin_comment_reply_script' );

function wc_enqueue_admin_comment_reply_script( $hook_suffix ) {
    
    if ( 'edit-comments.php' === $hook_suffix ) { // May need to add checks for product edit pages too if applicable

         // Adjust the path according to where you saved the JS file
        $script_path = get_stylesheet_directory_uri() . '/js/admin-comment-reply.js';
        $script_version = wp_get_theme()->get('Version'); // Use theme version for cache busting

        wp_enqueue_script( 'wc-admin-comment-reply', $script_path, array('jquery', 'wp-ajax-response'), $script_version, true );
        
    }
}