Jeff
I discovered the same thing the other day. Someone requested that I change the title of their post and I could do it as a moderator in my forum but when I tried to change the title of the thread in "Buy and Sell" I could only change it within the forum......does not show up in the thread.
I don't know if this requires special permission, but if you double click on the light part of the thread, on the gallery view, the box will become editable.