Let's say the Post Author is also the Administrator of the website. In this case, in the comment section, the user will have an "Author" label when he/she leaves a comment. 

To change the label you should use the hook code below:

add_filter("wpdiscuz_author_title", function ($label, $comment) {
    global $post;
    if ($comment->user_id == $post->post_author) {
        $label = __("Administrator", "wpdiscuz");
    }
    return $label;
}, 10, 2);

Put the code in the active theme functions.php file. This article should be helpful for you:  https://themaverickspirit.com/add-code-snippets-functions-php-wordpress/

The red-marked phrase can be changed as you like.