WordPress Remove "external" and "nofollow" from rel-attribute in comment author link

remove_external_nofollow_from_comment_author_link.php

/**
 * Removes the 'external' and 'nofollow' keywords from the rel-attribute
 * 
 *  @param string $comment_author_link The html link element
 *  @return string $comment_author_link Filtered html if the postauthort matches the comment author, else unfiltered html
 *  @author Ralf Albert
 */
add_filter( 'get_comment_author_link', 'remove_external_nofollow', 1, 1 );

function remove_external_nofollow( $comment_author_link ) {

  global $comment, $post;

	return ( $comment->user_id === $post->post_author ) ?
		preg_replace( '/(rel=["|\'].?)\bexternal\b|\bnofollow\b/', '$1', $comment_author_link ) : $comment_author_link;

}