It think such advertisements only attract people who are going to scam people here. Who else wants to buy and old account with a few posts? If it had many posts, the owner could earn some $ with it by advertising third parties in their signature. But that's not the case now.
Unfortunately the account's owners where so smart to not tell their accountnames. Bitcointalk should otherwise ban their accounts in my opinion.
Incorrect. The person who buys them and uses them for the wrong reasons should be banned.
Doing that you are fighting against symptoms of the problem instead of causes. By banning the buyers, the sellers still have made their profit and that would make this business attractive. But, I think it's easier to ban the buyers indeed, as the moderators probably can see an huge change in IP address.