Here's annother vote to keep things simple, although I'm not sure what that means.
Personally, I prefer reading through one forum for gear that's for sale or sold.
I do see value in a thread being marked sold and I see great value in leaving the prices posted.
Many times when I am considering selling an item or making a purchase, I scroll through those items for sale and sold for comparison sake. When the price is removed, we lose a helpful resource.