So first off, I don't know what prefix to choose it as so I chose site.

Anyway, it seems like only lmods are able to change thread names which is pretty weird because for example in the market thread, you title is listing the items you have for sale, once you sell an item you want to change your thread name but you can't, you would need to ask an lmod which would take time. I feel you should be able to change your own thread name or atleast have an option where you can ask to change the name to something then it would PM all the lmods ( or maybe one, I don't know) and then they can decline or accept the request, this way would stop people changing the thread to be something inappropriate or spam based.

When your thread is brand new, you can double click next to its name (when your on the thread list) and edit its name. If it is slightly older, you can edit your post and edit it's title.

but when you edit the title,it doesn't change the thread name,
only the header inside the thread,at least for me that's what it does.

Yeah I'm talking about being able to change the thread name later on incase you need to change it later on.

Supported.
I decided to name my replay thread "SkypePro's awful replays" and now regret it. Wish I could change that lol
Would be nice, and I don't see how this could go wrong.

You can change your name if you double click the thread title within a couple minutes of posting the thread. If you want your thread title changed after that, just report your post requesting that the title be changed. This may get changed to be a manual process on the user's end some time, but at the same time having threads have relatively constant names is nice too.