you can try with this:

http://developers.facebook.com/docs/reference/plugins/comments/

<script src="http://connect.facebook.net/en_US/all.js#xfbml=1"></script><fb:comments href="<?php the_permalink(); ?>" num_posts="2" width="500"></fb:comments>

add this script to the single.php where you want the comment box to be displayed

here is an example on how this looks like
http://leetsee.com/wp-questions.html