I'm not sure if this has been suggested or not, and with the suggestion thread closed, well... I thought I'd ask.
I would like to see a new feature that hides the reply button on threads that have been closed OR, threads where the user doesn't have permission to post. I know this would mean another look at the user permission before displaying the button, and it may mean another button needs to be created.
Okay... does this fall under the category of a mod?
Anyway... it's just one more "cool" idea that comes from the trenches.