It's actually quite hard to use these cross-tribe-chats. When I am talking with people on my own tribe, I can refer to the behaviour of other tribe members in chat. I can't say "Hey this person is dangerous" or "this person is fun" as you can't even crosscheck me or nothing.
I'd love to set something up where us 3 talk in future, but I have no point-of-reference whereby you can respond and say "Sounds fun".