WordPress paged-comments Plugin und duplicate content

<?php 
/*
Plugin Name: Seo Paged Comments
Plugin URI: https://www.tuxlog.de
Description: modifies title and meta tags to be different using paged comments p
lugin, to avoid duplicate content 
Author: Hans Matzen
Version: 0.1
Author URI: https://www.tuxlog.de
*/
 
/*
Copyright 2010 Hans Matzen
 
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/ 
 
// add filter to change title tag returned by wp_title
add_filter('single_post_title', 'seo_pc_title',399);
 
 
// filter function to manipulate the title tag
function seo_pc_title($title) 
{
    // check if paged-comments plugin is used
    $pl = get_option("active_plugins");
    if (in_array("paged-comments/paged-comments.php",$pl)) {
	// fetch commentspage from paged-comments plugin
	$pcno = $_GET['cp'];
 
        // rebuild title
        if ($pcno !="")
	   $title .= " &raquo;  Kommentarseite " . $pcno . " ";
       //let it out
       echo $title;
}
 
?>