steps for reproduction: 1) choose assault 2) get hide skill upgrade 3) go prone 4) wait until hidden 5) press the w key to start moving 6) left click you will unhide but you will not shoot
So why are you clicking the mouse if you want to remain hidden? Probably unintended behaviour, but the way to avoid it is laughably easy.
the way he describes it makes it sound like you dont fire the first shot after unhiding. also its a bug, its meant to be reported, its in the correct forum, he did nothing wrong ...
What he means is that pressing LMB unhides you, regardless of what the pressing caused. You can be out of ammo in your gun and when you click LMB you hear a click and become visible again.
Obviously hiding is some technowizardy that can sense hostile intentions. I don't get the second half, unless prone you should pop back in if you move around. This reminds me though, wasn't there a point where scouts used to be able to run for like 3 seconds if they crouch hide for a second? Maybe that was just scout hide, but I don't remember them popping back in from shooting or anything.