How could you practically apply a ban like that?
If you're caught attempting to buy or sell an account here, you would get banned. Whether a ban would apply to someone suspected of buying or selling an account, that's another story but it isn't rocket science. I'm not sure why people here make this out to be some sort of super-complicated dilemma, because it really isn't. The will to do anything by admins just isn't there. That's what the problem is.