I have friended most of you on forums, at least the big ones, that way I can find you on game.
Tonyy4's profile is hidden of course, but he still resides within a lobby. So on my friendslist, I can click on that anytime and go to that lobby. But I joined another lobby and immediately received about 100 xp. It isn't a to to high level players, but still very much free xp. Curious, I tried this a few more times. Out of all of them, it has only worked again once...
(Sorry by the way for abusing a bug, I just was curious and honestly wanted a little free xp, I've stopped swapping lobbies for now)