I think it is a bit of a double edged sword. If I buy something on a forum I will usually go back and let people know it's arrived. Almost like a feedback service on ebay. Now when an item sells and the item is marked sold, the thread is closed and this is no longer an option.
I'm not sure it's a good thing. Is it possible to mark items as sold but keep the thread open?
Might just be me thinking this.