One has to assume that if you post anything on the web, if someone really wants to find out who you are, and has some resouces and contacts, they can..that's why God created Lurkers..
This was not just his identity.
This was likely a CRIME, similar to someone having an illegally-recorded phone call.
The Post had a copy of an email (maybe it was a FReepmail?).
I'm thinking that a state employee put a keystroke logger on his work computer or spyware or an IT dept person collect detailed logs on his computer use. Either that or a recipient of the email/FReepmail was a mole or that person's computer was compromised by spyware or something else.