I am not affiliated with the development of this game. I do how ever have a lot of experience with how Battleeye and other Anti Cheat programs work. 99.9% bans are not for nothing. Your friend may have had something that was altering game memory in the background (injection software. hooks, or files where referenced against library of clean files, old method). Battle eye, if anything like vac will keep something similar to a .dat file of what was running while you are playing. So say he used something a couple of months ago and the program or script he used is now on battle eyes radar they would constantly cross reference those old .dat files and see that he had been running something in the past. Boom two months later a ban happens. My advice would be to have your friend contact battle eye about this situation. If he was cheating, injecting, moding then the ban was deserved.

There doesn't seem to be an issue with this for our group when we play. Have you ever run in a jacket let alone a military, medic of down jacket? I think they are going for extreme realism with the new updates. I played for a few hours yesterday and it seemed fine just take your jacket off. It would be nice if there where a layering feature like wear a long sleeve with a jacket and take off or add layers as needed.