LostSoul
Adventurer
Hit, damage, and miss, mean exactly what they mean in english. What happens as a result of those things, are what you write down on your character sheet. But the words are what allows you to imagine the action. If those words are meaningless jargon, because a hit is no longer the opposite of a miss, and a miss doesn't mean a miss, or a hit a hit, or damage results in harm done, then we're just playing a game with no independent reality.
I'd argue that the independent reality of D&D melee is very abstract, so much so that "hit" and "miss" don't have any real meaning.
Player: "I stab the orc in the face!"
(rolls to-hit: hit; rolls damage: 5 damage)
DM: "You stab the orc in the face. He takes 5 damage. He's still up and able to act without any penalty."
OR
Player: "I cut his head off!"
(rolls to-hit: hits; rolls damage: 5 damage)
DM: "You cut his head off. He takes 5 damage. He's still up and able to act without any penalty."
OR "I shoot him in the eye" "I cut his hand off" "I stab him in the junk" "I cut his belly open" "I cut his Achilles' tendon" "I pin him to the ground with my spear" "I break his arm" etc.
I'd argue that, in any of these cases, you miss your intended target. However, since the to-hit roll indicates a hit, you still do damage. Since you can miss but still hit, the to-hit roll only determines whether or not you deal damage. An ability that allows you to do damage on a missed to-hit reverses that, which hasn't been done before, but the effect is the same: you miss your intended target but still do damage.
'But you still hit your target, even if you don't hit him where you wanted to.' Sounds pretty similar to hitting a guy's shield or armour, which has traditionally been a miss.
Another way to look at is that no one knows what is happening in the game world until both the to-hit roll and the damage roll have been made. You can't clearly say what your PC is trying to do until after the roll has been made. You did 3 HP damage instead of 50, so you stab the guy in the leg instead of cutting his head off. (Which is probably on the edge of associated vs. dissociated mechanics. I think this is the default/standard mode of D&D melee combat, but I could be wrong.) In this case, there's no narrative or simulation difference; you did X HP damage, so narrate what that means as you typically would.
I'm not sure I like this mechanic because I'm not sure that you should always be able to deal HP damage, but narratively I don't see any issues.