The plugin will work automatically on either of the default templates. However, if you're using a 3rd party or you've customized it, the commentPreview DIV may not be showing up in the source code. Should that be the case:
You can have the commentPreview div show up where ever you want if you use the code
<?php live_preview() ?>
And this is where the div will show up in both of the WP default templates:
<?php doaction('commentform', $post->ID); ?>
Finally, if you've seriously changed the markup to your comment form (messing with ID's), then you may need to edit the plugin itself to match the ID's that you changed. They are stored in easy to change variables at the top of the plugin.
However, you most likely will not need to change any of this.
Thanks to Jeff Minard for developing this plugin originally and also to Iacovos Constantinou for his JS functions for parsing the comment text.




