Lounge<C++> frequently answers questions that are appropriate for the main site, and drive-by asking is a persistent problem. Lately there has been an increase in people coming to the room because they were banned from asking questions on the main site. Likely they find the chatroom by Googling the answerers they found helpful.
Would it be difficult to require such users to ask a room owner for permission? Already some rooms are restricted, this feature would just extend that to blacklisted users. Perhaps it should be opt-in or perhaps not.