Threaded Comment Feed Enhancer - Adds an info text in comment body from comment feed if it is a threaded comment

threaded_comment_feed_enhancer.php

<?php
/**
 * Plugin Name: Threaded Comment Feed Enhancer
 * Plugin URI:  http://torstenlandsiedel.de
 * Text Domain: threaded-comment-feed-enhancer
 * Domain Path: /languages
 * Description: Enhances the threaded comments feed
 * Version:     1.2.0
 * Author:      Torstenlandsiedel
 * Author URI:  http://torstenlandsiedel.de
 * License:     GPLv3
 */

/* Thanks to Dominik Schilling (@ocean90) and Thomas Scholz (@toscho) for many hints */

// Exit if accessed directly
if ( ! defined( 'ABSPATH' ) ) exit;

// Load Translation
function threaded_comment_feed_enhancer_init() {
  load_plugin_textdomain( 'threaded-comment-feed-enhancer', false, dirname( plugin_basename( __FILE__ ) ) . '/languages/' );
}
add_action('plugins_loaded', 'threaded_comment_feed_enhancer_init');


// Add info text in comment body if there is a threaded comment 
function threaded_comment_feed_body_enhancer( $comment_text ) {
  
  if ( ! is_comment_feed() )
    return $comment_text;

  //$comment_object = get_comment( get_comment_ID() );
  $comment_id = get_comment_ID();
  $comment_object = get_comment( $comment_id );

  if ( ! $comment_object->comment_parent )
    return $comment_text; 
  
  $parent_comment_object = get_comment( $comment_object->comment_parent );
  $parent_comment_link = get_comment_link ( $parent_comment_object->comment_ID );
  $parent_comment_author = $parent_comment_object->comment_author;
  $parent_comment_content = $comment_object->comment_content;
  $message = sprintf( __( '(This is a reply to the <a href=\'%s\'>comment</a> from %s.)', 'threaded-comment-feed-enhancer' ), esc_url( $parent_comment_link ), esc_html( $parent_comment_author ) );
  $message .= '<br><br>';
  $message .= '<blockquote>' . $parent_comment_object->comment_content . '</blockquote>';
  $message .= '<br><br>';
  $message .= $comment_text;
  return $message;
}


if ( get_option( 'thread_comments' ) ) {
  add_filter ('comment_text', 'threaded_comment_feed_body_enhancer');
  add_filter ('comment_text_rss', 'threaded_comment_feed_body_enhancer');
}

?>