Last I heard, Bitcointalk was preventing people from registering who were using known Tor exit nodes, but not blocking registered accounts which were accessed through Tor. (Not quite sure on this, would like to see someone to confirm)
Nope, its just that the IP addresses from known Tor exit nodes tend to have a lot of "evil points" which require a fee in order to create a new account. This is not related to Tor and any IP can collect these points. Spammers usually use Tor/VPNs to create accounts though. If you know someone that is allready well known here, that person can also vouch for you and contact an admin/mod to add said new account to a whitelist.
Edit: Fee for evil points is usually small. See here[1] for more.
[1]
https://bitcointalk.org/index.php?topic=772564.0