Source

File: wp-includes/comment-template.php

function get_comment_author_link( $comment_ID = 0 ) {
	$comment = get_comment( $comment_ID );
	$url     = get_comment_author_url( $comment );
	$author  = get_comment_author( $comment );

	if ( empty( $url ) || 'http://' === $url ) {
		$return = $author;
	} else {
		$return = "<a href='$url' rel='external nofollow ugc' class='url'>$author</a>";
	}

	/**
	 * Filters the comment author's link for display.
	 *
	 * @since 1.5.0
	 * @since 4.1.0 The `$author` and `$comment_ID` parameters were added.
	 *
	 * @param string $return     The HTML-formatted comment author link.
	 *                           Empty for an invalid URL.
	 * @param string $author     The comment author's username.
	 * @param int    $comment_ID The comment ID.
	 */
	return apply_filters( 'get_comment_author_link', $return, $author, $comment->comment_ID );
}