Hmmm... yeah, don't really want to grant moderator permissions to everyone.
Is there any plans to change this? Every other forum software I have used in the past allows users to edit thread titles (with the proper permissions, of course), and it's a handy permission function to have.
One big example is for sale threads - if a forum has a marketplace where people buy and sell goods with each other, it is useful to tag the thread titles in some consistent manner, such as [WTB], [WTS], [BOUGHT], [SOLD], [CLOSED], etc. That way, people aren't clicking on useless threads, waiting to see whether the item is actually still for sale or not. Obviously, moderators can edit the thread title, but that puts unnecessary load on the moderators of the forum. It is also much more convenient for the user to do it themselves, since they can have it take effect immediately after the status of the thread changes.
I do hope that you will consider changing the thread title to be part of the edit post functionality in the future, instead of part of the moderator toolset.