Well, how many people are really open-minded enough to discuss religion?

I would imagine you'd get little more than people ranting about/defending their own beliefs (and that includes atheists).

There used to be a really great (traditional Western style, logins, etc) board called Religion Talk. I guess it's still up, actually, if this is the one I'm thinking of: http://religiontalk.org/

Here, though, I doubt we have the kind of users who would really want to do research and discuss religion from the perspective of learning about other people and cultures. We'd just get "debates" and it would be walking up the down escalator to nowhere.