While I am not really in favor of open chatting in this game (it would allow for massive trolling), it would be nice if friends could send each other messages. This is also linked to the following:

I see some friends (non-FB) play illegal formations continously and they lose or draw matches they shouldnt. It bothers me that I can't message them to tell them this or that the game itself doesn't warn them of illegal formations. Only people on these forums know about illegal formations and their rules. That's a bit silly. Not to mention the idea itself of illegal formations is silly.