I've only seen the close thread thingo on ikonBoards and other places like GameFAQs. The starter of the thread is the only one who can close obviously.
...or can regular users not close any threads, even their own? That would be pretty stupid if true.
Well it seems like it is quite stupid then. I've looked in a thread of my own, and can see no "close thread" button, nor any other button that isn't there in a thread not started by me.