This plugin allows you to quickly and simply display the number of words in each comment on your WordPress website by simply adding this template tag into you themes comments section:

<?php comment_wordcount(); ?>

Because this only shows an integer you would need to add any preceding or following words that you want shown after the template tag has been called. For example:

This comment has <?php comment_wordcount(); ?> words.

If you have any problems with this plugin or need any assistance feel free to contact me using the contact form that can be found here. I will try to reply to your query as soon as possible.