Yeah, it bothers me too, a thread going off topic. I have to decide whether I want to keep a thread on topic, or actually communicate. In the past, on this forum, I have erred on the side of communication, because I know how EASY it is to split threads in civfanatics. Problem is, apparently, there is no active moderator for C2C. I think that is the real problem. Not off topic posts, or the difficulty of splitting a thread, but lack of administration. I assume that it existed here, once, but people have retired or fallen ill or moved on. Maybe it is time to ask that someone else have mod privileges for this sub forum. At least until one of the adults comes back. Or, on the other hand, get a current mod to agree to upkeep duties like that. I've seen here on civfanatics, someone just @'s the mod, asking them to split from post X to post Y into a new thread entitled "ZZZ", and if they recognize the person and it doesn't seem stupid, they do it. Takes seconds of their time.
Though, that has been a while... maybe things have changed?