I really don't get how this topic gets so misinterpreted by many..
If you login into a website while using TorBB and that website has your true
IP for you already logged in not using any encryption (VPN, Tor), one time is
enough, then for sure the owner of the website has a very easy job at
identifying you.
Remember: one time is enough, even if it was say 5 years ago - if the owner
of the website keeps logs indefinitely, he can very easily find the IP with
which you logged in that one single time with your real IP. Then the matter
of finding name and surname is trivial, all it takes is one call to your ISP
(they do keep logs, and for a long time, in most countries AFAIK).
If you create an account for a website while in TorBB and you **always**
login and use it with the TorBB then you are anonymous.