As I said, you can just display the thread's name a user last saw, and not the other.
You don't really seem to understand the consequences of this suggestion. You seldom seem to even understand your own suggestions. So if we would allow the thread name change - the thread get's changed by user, get's changed by GM, user can then again change it. The loop continues. There is absolutely no need of this. For gods sake, this guy needs a cooloff from forums. Atleast a warning would be long overdue.
As you said, a need for changing a thread's name is rare, so flooding will not happen.As I said, you can just display the thread's name a user last saw, and not the other.