Mat,

As Enoavidh points out, it means Your Mileage May Vary (Americanism,
meaning you might have different opinion). I certainly don't check the
validity of poster's emails in most cases, I was just pointing out when
someone comes out of nowhere with controversial opinions, if they don't
have a a more concrete persona than a Usenet tag it might not be worth
arguing with.
As an aside, it is a time-honored tradition of Usenet in some
circumstances to "take it to email'. Your choice, but you might chose
to set up a free "public" address (yahoo, hotmail, etc) in case anyone
tries to communicate offgroup. Or not, if you prefer.
In any case my comments re real names and addresses were mainly
directed at troll-like posters.