Via PM'ing, I've had any number of great & ongoing conversations with other members of this forum. There's lots of fantastic people here, and it's been a real treat to get to know some of them better on a personal basis.
OTOH, I've also had some very
unpleasant surprises, from people from whom I expected it least, up to and including requests for pirated software. (And that person had better know what I am talking about, and feel ashamed

)
These varied experiences leave me with mixed feelings about an off-topic forum. At most, I would be extremely cautious about adding such a thing. I agree with Mitharheru that it sounds like a great idea, but if it were to be done at all, experimental (whatever that turns out to mean) would be best at first. I'd also point out that the Tolkien forum --another potential avenue for off-ToME discussion-- has seen very little use, despite all our mutual interest and devotion.