I would love to see something like this implemented. Although if it is implemented, then their sale/buying activity will just eventually start leaking out to other sections of the forum, which will create a lot of off-topic posts and spam.
I have my own personal policy anyways, which is to almost never deal with a newb in the first place. Each person can have their own internal filter, so although an official policy would be nice, I don't see it too necessary. What OP said is true though: most forums do not allow new accounts to do business until they reach a certain post count.
Newbie here, very late to this party and still finding it difficult to get started.
You can thank your other fellow newbies that are out only for a quick scam. There are just too many of them, and it ruins it for the rest of the legit newbs.