I'm assuming you're just seeing that text? If so, that's usually caused if you don't have the JFBCSystem plugin enabled. Other possibilities are if the module is being loaded over AJAX in some way. If so, and whatever is loading the module dynamically isn't using the full Joomla flow, the JFBCSystem plugin may be skipped. That plugin is where the tag replacement happens, so if it's not executing, that's the problem.
If that doesn't help, can you post, or Private Message me, a URL of a page where the comment box isn't working? You can PM me by clicking the arrow under my picture (<----) and hitting the mail icon.
Thanks,
Alex