I think the threads in the bugs and wishlist section being closed is a bug, or at least they were not meant to auto-close.
At the bottom of this thread there is a note stating the thread will auto-close after 1 month without replies. But this note is not posted on bug/wishlist items. So I think it is not intended to auto close, which makes sense. Auto closing those threads wouldn’t make sense.
edit: I may have found the cause. A couple of days the admins of this forum opened a new section for bugs. This one does in fact have the auto close option and note enabled. The old bug forum didn’t. Neither does the wishlist section. So I guess it’s a matter of removing the auto-close flag in the settings.