Updated 16th May, and should now work fine with WordPress 2.2. Please report any bugs if found!

In order to get the Quicktags add-on displayed above your comment form start by downloading a copy of comment_quicktags.zip, unzip it and upload the 2 files to your theme directory:

Download comment_quicktags version 1.1

Second, (-> WP2.1) add the following to your theme’s header.php:

<!-- Include the Comment Quicktags -->
<script src="<?php echo bloginfo('template_directory') ?>/quicktags.js" type="text/javascript"></script>
<script src="<?php echo bloginfo('template_directory') ?>/comment_quicktags.php" type="text/javascript"></script>

Then replace the existing textarea paragraph in your theme’s comments.php with this:

<p><script type="text/javascript">edToolbar();</script>
<textarea style="width:99%;" name="comment" id="comment" cols="70" rows="10" tabindex="4"></textarea>
<script type="text/javascript">var edCanvas = document.getElementById('comment');</script></p>

Finally, open styles.css in your theme’s folder and add the following lines (anywhere):

/*** QuickTags on Comments (Plugin styling) ***/
#commentform #ed_toolbar input.ed_button { width:auto; }

Enter one of your posts and refresh your browser window. You should now be able to see the Quicktag add-on above the textarea where comments are entered.