Personally, I find it really weird when I tag someone and a "@" comes up, it looks silly. If there is a valid reason for it being there, then fair do's. However, I would like to see it removed as it doesn't really make a difference if it is there or not, the user is still tagged and it makes the tag look cleaner. It can be removed via the Admin CP > Options > User Alerts >
It used to be different, I have no idea why it was changed. Hopefully whoever changed it can see how Vintage_Gamer looks better than @Vintage_Gamer.
But then if you want to say someone's name without tagging them it becomes a hassle, typing in an @ symbol isn't difficult.
I also like the @ when tagging. It makes it explicitly clear that people get tagged. Otherwise it just looks like a normal link. -1