feel free not to join if you dont want to. I for one dont wanna open sins to sit in lobby wating for someone to start a match that I would want to play in. Id rather be doing work or something and send a few messages to see what we want to play rather than alt tab over and over in the sins lobby trying not to miss a match or a friend online.
also, sometimes i may be playing another game alone, people can check and still ask if i want to mp, and then maybe ill join
so, as i said, feel free to join
as for IRC, i agree with nephilim, it doesn't allow as much as xfire