I have exactly the same problem there. Its the double edged sword of tracers, its good to see what your hitting but twice as irritating when they dont call it. I do find though that most people if I point out nicely that they had been hit tend to take and go back to regen. If they dont then I aim for the parts they cant ignore.
I often wonder what is happening when someone doesn't take their hit. Guess it depends on the player as i've told a mate once or twice he has been hit in the past year or so as I heard it but i'd assume he didn't and i'm confident he wouldn't shrug a hit off if he was aware of it.
On Sunday I heard the distinct noise of a shot hitting a chaps chest rig, he didn't take it but took the second shot. Later that day a player rushed me, lacing up the cover I was behind but missed me, he then hit the ground 5-10 metres away from me. I put my rifle on the ground, drew my pistol and fired a few rounds and hear the sound of one hitting fabric(almost certainly on his calf for reference). I heard no call of "hit!" so I said "mate I heard that hit you" at which point he took the hit.
I think the thing to note is that we all miss the odd hit. I've had two instances since I started of a marshal telling me I was hit when I wasn't aware of it(although one I am almost certain it hit another play, but I took it without question anyway) - What I mean is give the player the benefit of the doubt unless it's consistent
One thing that does concern me is the rise of recording game footage. Fine in itself but when the footage is used as a witch hunt it all becomes very iffy.
I played a game recently where we were told that a sniper had footage of a player not taking hits and if they ID'ed the player they would be banned. Issue with this is that you don't know if it is a case of a player neither hearing nor feeling the shot and also I'm sure I am not the only one that has jumped as a shot whizzes by them which could be misconstrued as flinching(you will reflexively move away from the direction of the shot as if you were hit)
I am actually quite concerned that jumping when you are taken by surprise could be taken as conclusive proof that, actually you flinched and as such are a cheat.
I am all for politely telling people they have been hit though. It's something that is only sensible to do within earshot so you aren't shouting across a field. It all depends on how you phrase it, and bizarrely the only time I have had the player disagree is when I saw multiple BBs bounce off them at close range. At that point it meant they have hit me by blatantly cheating so I just take the hit and carry on with the rest of my day.
