On Xbox you can tell who's on PC because they don't have a picture.
One question I have, is that PC is still cross-play with PS4, and the X1. How the hell does it separate between both and not have cross-over?
You only can communicate through quick chat.
"Nice Shot!"
"Thanks."
In matchmaking if it selects an XBO user then it sorts the others out. If it selects a PS4 it sorts the others out. So apparently it depends on which hits your party first.