I hate the word cheaters. I especially hate that word when used towards somebody who adjusts "ingame" settings through the menu options. To me a cheater is one who actually installs a script (script kiddies anyone) or some such "extra" in the game files to alter his gameplay.
Tweaking "ingame" options is there for a reason.
I can honestly say that the only time I have ever changed an .ini file was to "fix" a lack of widescreen capability. Is that cheating if others have not done the same?
As to the OP and hiding in the dark, to what end does this accomplish the objective you have been given in the mission briefing? What are you defending, if that's what you are doing? And finally, if I am shot from out of the dark more than once or twice and I figure out where you are lying in the dark, I can guarantee I will be telling my team mates exactly where you are laying in wait. Maybe that's what is happening and it's time you come up with a different strategy, eh? You shouldn't assume that everyone who shoots you in the dark might be cheating, maybe they are using teamwork and are trying to get you to change your game.
I have often wondered how some players can do what I call pop up head shots. You know, they pop up over a window sill or wall and pop back down. They do this 2 or 3 times, then on the 3rd time, they head shoot me, even if I move a bit from their view...is that cheating or an exploit because I don't know anyone IRL that would risk something stupid like that AND actually pull it off.