Oh, that is a nice feature actually, but i still can't understand how the accounts OP bought got blocked if that is how it works. The seller would not lock the accounts if he already sold them.
1. Seller sells a hacked account.
2. Buyer gets the account, and changes email/password so seller can't access it anymore.
3. Bitcointalk sends an email with link to lock it to the original owner.
4. Original owner locks the account.
(5. Buyer opens thread to complain)
(6. Seller hacks the next account and continues his "business")