I think the chat box should be seperated from the actual screen were the character moves, so that the character doesn't go all beserk when you go to say something.
Although, it is probably just the demo that's like that, I think it should be put out there none the less.
Only Mt. Hildar will have this feature. It's the MMO part of TMJ, so of course you can chat. It's easily solved though, it's not a big enough problem to worry about.
PVP battles will be included, you will definately be able to view your own stats, but checking others stats is uncertain at this point. TMJ is a traditional RPG, the MMO is only a small part.