Honestly I don't think a child would think anything different from actually real fun or friendship. Besides it is text only, don't contain nudity or anything related to adult content.
If it really bothers you I can try to block this one also but I really don't think a child would understand it like you did. To tell the truth, I'm not sure would also. There are real chat sites out there. Not that they don't have adult rooms (I suppose they do) but I guess it would be made in a way to be safe for other ppl to use it. I don't know. I'm trying to get an even larger picture. ;-)
Nabble staff. We never ask for passwords.