A IMHO thread was just closed by a mod, apparently at the request of an OP.
Why is this permitted, particularly when the forum was IMHO? I sincerely don’t get it. I might understand this on another message board, but it seems to fly against the alleged purpose of this board.
Well, to start with the obvious, a poster is certainly allowed to ask a Moderator to close a thread, whether one that he/she started or another. The question is whether the Moderator will comply with the request.
There are lots of reasons for agreeing to close a thread, and lots of reasons for not agreeing. So, it all depends on circumstances. For example: A request to “Please close this thread, because I don’t like what people are saying” will almost never be honoured. A request that says, “Sorry, I opened this thread in IMHO before I realized there was a similar thread,” might be honoured. “This has become a free-for-all trainwreck” might be honoured, as well.
If you want to know specific circumstances for closing a specific thread, ask the Moderator by email.
Fast response; that’s good service. 
Thanks.