What can be done about using proxy servers?

A new (at least new under his current user name) poster made a series of posts on TS/S today. Some were obscene. Others were personal attacks. One bragged that "This is my third time posting. I will continue to post (via Tor, an anonymizing proxy which others use and therefore can't ban without banning them) until I get an answer. Until then, .... off TSA pedophile sympathizer."

Does FT have a system to identify posters who use proxy servers? If not, perhaps the best answer is not to allow any posts at all from these servers.

There is no point in having a TOS at all if use of a proxy server will allow anyone to get around it.