There are more elegant ways to display to the player that they're dealing damage. If you look at Reach specifically, it never needed HUD-based damage feedback like that because of the really spectacular way they designed the shield flare - as players take more damage their shield gets brighter and becomes greater in volume, increasing the bubbling effect proportionally to their shield level (this worked in the same manner, only backwards [bright to dim], when the shield was recharging, making it an incredibly intuitive analog system with very easy-to-understand rules). You could tell whether someone was 3-shot or 2-shot just by looking at the brightness of their player model. Going away from that and to a more blunt method of conveying that information was a real disappointment. It was almost a requirement in Halo 4 though, as the shield feedback was a big step back, partially because of its very washed-out look that made contrasting players and their shield from the environment more difficult than it had been previously. Looking at H2A, it doesn't seem to suffer from that contrast issue, so the hit markers just seem unnecessary.
It's something I'm against on a sort of academic level, because even though it's not actively damaging or anything (though I think it absolutely makes players lazier, specifically when applied to grenade impacts), there are much better ways to get that information across.
