Hey Peter,
can you disable plg_system_eprivacy?
I see that it is adding this code to the page:
<script src="/media/plg_system_eprivacy/js/jqclass.js" type="text/javascript"></script>
<script src="/media/plg_system_eprivacy/js/jqurl.js" type="text/javascript"></script>
<script src="/media/plg_system_eprivacy/js/jqeprivacy.js" type="text/javascript"></script>
And in the jqclass file it seems that they manage to improperly override the mootools Class object. And since they do this, ccomment no longer works. Please disable it and see if the comment system works after that. Or let me inspect the page again when it is disabled.
Regards,
Daniel