No it's not. You can't stop people selling accounts just as you can't stop people from scamming. It's also already easy to retrieve accounts and there's nothing to stop people from selling an account and then trying to get it back as we can see from this exact thread.
Why hasn't it retrieved yet in this case, then?
If you ban this and strictly return accounts once they are proven selling will mostly stop. You're providing protection to the buyer which makes it possible in the first place.
It wont stop just because you say it will. Theymos probably has better things to do than deal with the fuss of returning accounts and can be quite lax on returning them, not to mention
this situation isn't as easy as giving the original owner their account back because it looks like it quite possibly shouldn't be returned to him. Whether account selling is or isn't allowed it won't stop and situations like this will always happen. 2-factor is desperately needed though and hopefully that will cut most hackings down when it arrives with the new forum.
If account trading was banned the situation would have been easy. You see the difference?
If a buyer knew that the seller can easily get it back, the market will reduce. That will decrease hacking too. You are going about handling the problem the wrong way.