This issue has been discussed before on meta.SO, however, I think it needs revisiting. Originally, the idea of disallowing new users to chat was in order to prevent SPAM and also to make sure that the question gets answered in the way that other people see it. However, as we all know sometimes follow-up questions must be asked/answered in order for the question to be answered at all. Indeed, StackExchange implemented the "Would you like to move this to chat automatically?" feature on long comment exchanges, yet new users cannot talk in chat. This can be problematic because chat is sometimes the easiest way of actually getting to a point where an answer to a question can be posted at all. The tension between having long comment exchanges and having chat can be resolved if we allow new users to chat.
Nonetheless, the threat of SPAM and off-topic remains, though the latter issue is moderated by the gamification: there is no rep for solving problems on chat. SPAM is a potential issue, but not unsolvable one: Some possibilities:
- Have a single chat room just for new users, only accessible after a post has been made. SPAM bots can have their fun in the new user playroom.
- Chat room invitations: an established user (say 200 rep? 500 rep?) can invite a new user to a special chat room. If the user turns out to be a SPAM bot then the chat room is shut down when the established user leaves.
I think allowing some form of chat for new users will not fundamentally change this as a question/answer post oriented-site, and allow more questions to be answered in the first place.