I'm waiting for seller. Who will return me my money?
The seller probably won't even return your money. Why? They're a hacker in the first place who sold you a hacked account.
Why the selling of account is allowed?
Look at this thread:
https://bitcointalk.org/index.php?topic=703657.018. Having multiple accounts and account sales are allowed, but account sales are discouraged.
That being said, you're probably a newcomer who sees the opportunity to make money from this forum and took a shortcut. Just like what KWH said.