I realize this has been present since ARMA 2, but with the lighting improvements to the new engine I would have thought there would be changes to how light collides with objects.
When shining a something like a flashlight, muzzleflash or chemlight at a building, rock, etc, the light shines through. This causes a major problem for things like nighttime missions, as traversing through urban streets with a flashlight on would cause the light to shine through buildings, and could then be more easily seen by players, enemies, etc. {F17895} {F17896} {F17897} {F17898} {F17899} {F17900} {F17901} {F17902} {F17903} {F17904} {F17905}