How override the comment template

Hi, I want to use a different template to show comments (for a single post), in order to add a button/link near the “reply” link, for each comment.

So I have copied comment-template.php from the wp-includes folder to the “templates” folder of my plugin, in order to edit it without editing the wordpress core files. Then I have added the following lines in my plugin:

add_filter( 'template_include', array($this, 'pf_comment_template'));

with the following function:

function pf_comment_template( $template ) {

		if ( is_single()  ) {
			$new_template = dirname( __FILE__ ) . '/templates/pf-comment-template.php';
			if ( '' != $new_template ) {
				return $new_template ;
			}
		}

		return $template;
	}

But I get the error:
Fatal error: Cannot redeclare get_comment_author() (previously declared in ….\wp-includes\comment-template.php:22)

How can I solve?
Thanks!