Our concern about chats isn't that someone might use a four-letter word. It's that someone might get molested after arranging a real-life meeting.
We hope that you aren't that stupid, but all it takes is once. Even if we didn't get shut down officially, nobody's parents would let them use Snap! any more.
And so if we allowed chats, we'd have to watch them closely. And that's not how we want to spend our time; we'd rather help people learn computer science.
So, no. Sorry.