Implementing “No Duplicate Comments”

I downloaded no duplicate comments and activated it. According to the notes at this site:
http://www.coffee2code.com/archives/2005/03/30/plugin-no-duplicate-comments/

I need to use the following function:

function c2c_no_duplicate_comments ( $comment_text )

But I don’t know where???

I opened up comments.php in folder of the theme I am using, and the most likely place I think is round about the following area:

// <? // Begin Comments & Trackbacks ?>
// <?php if ( $comments ) : ?>
//
// <? // Begin Trackbacks ?>
// <?php foreach ($comments as $comment) : ?>
// <? if ($comment->comment_type == “trackback” ||
// $comment->comment_type == “pingback” || ereg(“<pingback
// />”, $comment->comment_content) || ereg(“<trackback />”,
// $comment->comment_content)) { ?>
//
// <? if (!$runonce) { $runonce = true; ?>
// <h2 id=”trackbacks”>Trackbacks & Pingbacks</h2>
// <ol id=”trackbacklist”>
// <? } ?>
//
// <li class=”<?php echo $oddcomment; ?>” style=”padding:
// 10px;” id=”comment-<?php comment_ID() ?>”>
// <?php comment_text() ?>
// <cite><?php comment_type(__(‘Comment’),
// __(‘Trackback’), __(‘Pingback’)); ?> <?php _e(‘by’); ?> <?php
// comment_author_link() ?> — <?php comment_date()
// ?> @ “><?php
// comment_time() ?></cite> <?php
// edit_comment_link(__(“Edit This”), ‘ |’); ?>
//

// <?php /* Changes every other comment to a different class // */
// if (‘alt’ == $oddcomment) $oddcomment = ”;
// else $oddcomment = ‘alt’;
// ?>
//
// <? } ?>

(Note: I put in the ‘backsticks’ on each line above as instructed! 🙂 )

Can someone please point me to where it is I need to put the function? There is also a file called comments-popup.php. I figure I need to also put the function there, right?

Or do I need to find where the function for comments are called in the index.php or some place else?

Thanks a bunch!