B.A.R = Browning Automatic Rifle. Even Mr. Browning didn't call it a MG.

English language uses very broad terms with weapons, it uses term machinegun in association of automatic pistols (SMG). This can become a wee bit confusing at times. In any case I am used to call those weapons automatic rifles, not machineguns. That much about my definitions in my language.
It may have been an "automatic rifle" but it served the role of an LMG for the US troops. Automatic, rifle ammo, fired from a bipod, etc.
But by your definition, Minimi can not be a LMG. It has a belt as a primary hasn't it? Same goes for weapons like RPD, PKM, MG4, M60, M240 or the KVKK 62 seen in the video. I beg to disagree with that as well.
Ah, I see. I wasn't taking modern weapons into account.
Also in WW2 German machineguns integral to the rifle squads did use belt as a primary means of feeding the gun. Or have you ever seen a German fighter who is carrying 10 drum magazines? And how many times have you seen a MG'er or his assistant with a belt of ammunition?
Yeah, like I said the Germans are kind of the odd ones out here. They built the squad to support the machine gun, whereas everyone else used the machine gun to support the squad. LMGs weren't all that popular with the Germans when they could set up an MMG that was a hundred times as lethal.
About supression one must seperate real life and game. Supression in RL is to prevent someone doing something. let us take a door as an easy example. You do not want to have anyone coming through a door. Solution: you shoot through the door a single shot with a second between shots. Doorway is suppressed and no-one will be poking their noses out during the duration of the suppression because they know that the doorway is under watch and fire... Things like this are done to allow own movement or prevent enemy movement. This is just one example.
In game, one may choose differently because game is game, not reality, and there will not be that much coordination anyway. Also it helps that no one really dies, too.
Question: Are you -only- shooting through the door when you know that someone's there? I do that too. Like I said, if I sense enemy movement I don't have any problem letting a few fly to try and penetrate their cover and let them know they're in my sights. If you're pumping rounds into the door just to keep people from moving past it even if you don't know there's anyone there, I have to strongly question the strength of that strategy.
You misunderstood me somehow. If you have a clear sight of the enemy of course you are going to shoot him.

I am talking about things like seeing an enemy popping out of cover and then him returning behind cover. You dont see him anymore but you know he is there and a Mg gunner would suppress him, and the enemy would not engage in anything other than seeking some better cover or staying where he is. That would allow an mg gunner to acquire new targets as he would know that this one is "taken care of" for a short period of time. Doing that in game is pointless as you only give away your position and the enemy gets a gray screen that does not hinder him in any way and he can easily return fire.
Well, like I said a few posts above you there's nothing wrong with letting them know that you're in the area and that you see them, but then -stop firing-. Put a few rounds as close to them as possible, and then go dark. If you keep firing, it only lets them know where you are, whereas if a bunch of bullets whiz past their face right as they're about to round a corner (or if the guy in front of them gets torn to pieces by MG fire) they aren't going to know where you are, but they will know that you're there. They can't fire back at you because they don't know where to shoot, and they have to try and peek out, ample opportunity for you to kill them.
If you keep shooting, your accuracy degrades enough for them to peek out and spot your muzzle flash. Then it's just a matter of putting shots on your hidey hole till you're suppressed or one hits you.
You should be a presence, you should be scary, they should not want to keep going once they know you're there. But the scariest thing is to hear the MG, to see his bullets kicking up dust inches from you, but to not -see- the MG. There are times on Spartanovka especially (thanks to the map clutter), where I can hear the MG34 firing what sounds like 20 feet away from my position, but I still can't see him and he's gunning down all of my buddies. It's terrifying. I don't want to move from my spot, as the only way I'm still alive is because he hasn't seen me yet. I'm desperately trying to find him, but I don't want to risk getting shot as I peek out to try and get a fix on his location.
TL;DR - Let them know you're there, but not where you are. Area denied.