Use this code to modify the author says text on your site

author-say-text.php

<?php
/**-------------------------------------------
* @package Bulk Studio
* @link http://bulkstudio.com
* @author Rhythm <rhythm@bulkstudio.com>
* @copyright Copyright (c) 2013, Bulk Studio
-------------------------------------------------*/
/** Modify the author says text */
add_filter( 'comment_author_says_text', 'custom_comment_author_says_text' );
function custom_comment_author_says_text() {
    return 'Your Text';
}