Imagine you've created a thread on your forum, you then promote/push it via share/like/recommend to FB.
Is there any way to prevent comments on that story/link on FB, therefore directing the comments, interest and traffic back to your site?
I see this as quite a stumbling block because the Facebook user is already on the FB article with a reply box handy...which is easier? Comment on FB now, quick as a flash or think hmm, maybe I'll add comments to the same thing again on both FB and the site?
The answer is simple: the user is bound to use FB as the commenting ground, which could may well leave you with a singular forum thread with many views (maybe) but little or no responses.