Discrimination against PS4 users?

[Felis]

And how would they KNOW? You LITERALLY can't know unless you're on PS4 aswell.

While they don't know if someone play on PS4, there is a hint to know if someone play with a controller.
Running left and right with side steps and doing backsteps - mostly a keyboard player
Turning the body to the direction of the run - mostly a controller player (legacy control on controller is just so much better than standard control)

Aside from the controlling issues (I hate the controller gameplay in this game), I can only spot PS4 players by them being stuck longer in loading instances or watching cutscenes longer due to quicker loading from my SSD.

That only allow you to spot HDD users. You can change the HDD in a PS4 with a SSD.