Wow, what a lot of each side of the fence. I have to sit both sides on this one, myself. I've been known to play similar online games and honestly the characterization can be fun. I haven't before heard of a term given for leaving out personal info while playing, but... okay. *shrug*
On the one hand, I totally get the "individual" thing. I know that most of the "guys" online don't have a thing to say to me if I mention up front that I'm a happily married mom with two kids. However, after a while, the ones that talk to me more will learn who the person behind the character is, and I offer that information up pretty quickly so there's no misunderstanding that something is headed in a direction anywhere other than just friendship.
If he's still in the beginnings of the game and wants to be known for his "character" online, that's one thing. Anyone he's giving his email out to, however, is likely someone he ought to fill in a few details for, to be sure there's no misconceptions, in my opinion. I've had fantasy "characters" get "married" to the characters of friends I've made online - however they've always known that it was all just a fun, fictional, game and nothing more - and fairly early into the game too.
The other factor that I get concerned with, however, is how much time these games can take away from real family at home. While I can walk away from the screen nowadays, these games can quickly suck away hours of time if you let them. I know my husband has trouble NOT playing these games once he gets started on them and so we only play when *I* say it's okay, after the kids have gone to bed. I don't want my kids seeing some of the violence portrayed on the screen at their current ages, and I want my husband to be engrossed in our kids, not some game on the computer. So we limit how often and when we play so that it can be a fun extra in our lives instead of virtual black hole for all our spare time.
I wouldn't be overly-worried about it, but I would sit down and talk to him about your concerns. While I know what it's like to want to seperate oneself from the day-to-day grind of things, at the same time he won't want to make things complicated by someone misconstruing anything. He may want to be forthright with those he builds closer friendships with, especially if it will help you feel more comfortable.