Just to add on what Yahoo62278 said, others could just be scammers claiming to have an account for sale yet they actually don't. They afe just waiting prey on anyone stupid enough to trust them.
I think no one uses this method to cheat, it's not optimal 
Everyone knows that buying an account will involve a lot of security, they won't be stupid to lose money, the escrow is always chosen for safe.Not only on this forum, bitcointalk accounts are always available out there, intermediary trading sites. If I remember correctly, I have seen a few people selling accounts on bitify. They are expensive and have no information
There are many websites like https://selly.io/ where people are selling these accounts and I am sure these are fake accounts. There is no way to know in advance, if the seller will scam you after payment or really give you the account.
Since the introduction of merit, very few accounts attain Sr / Hero Member status and no ones sells their precious accounts.
Yes. Bitcointalk account selling on many websites. But buying an account is risky. The seller does not get caught. But the person who buys the account has a chance to get caught. And if he gets caught, his account may get tag from DT member. So those who buy bitcointalk account, they have higher risk.
The seller gets the money but the buyer will get caught eventually. The writing style changes when the buyer buys the account and starts writing in his own style. Sooner or later it will be identified. Also if an account previous owner was posting in some local section and all of sudden the new owner start posting in another language in another local section, will also indicate the change of hands with the account.
