For example I have 7 posts (now) I have had 2 scoobs in the past, been a member on TTS years ago as vantastic, scoobynet etc, know lots of people in the scoob world, sure a Mod could run the for sale area and look at the posting member
I voted post count, but this is a hard call, you could miss a bargain just because someone has joined to sell something!
I see all the points, but sure any member will look as the seller and trust an active member more than a 1 post member selling something