Confirmed as a genuine gap rather than a bug.

You are right about what the item is meant to do — the Heart Chocolate from that quest is a death-protection charm in v83, the same family as the Safety Charm: when you would die, it is consumed instead and you are revived on the spot. We have no death-protection mechanic implemented at all, so right now the item exists but does nothing when you die.

That is real work rather than a one-line fix (it needs a hook at the moment of death that checks for a charm, consumes one, and revives you instead of showing the tombstone), so I am marking it confirmed rather than pretending otherwise. It is worth doing — the same hook covers Safety Charm and the Wheel of Fortune.

Half right, and the half that's wrong is Nexon's fault rather than yours. The quest dialogue really does promise that the chocolate "will protect the owner for 3 days" — but that promise was never implemented: Heart Chocolate (item 4140100) is not a death charm in any v83 server we have. All of them hard-code the same three items for that mechanic, and it's the same list in every one: Safety Charm, Easter Basket and Easter Charm. Adding Heart Chocolate would mean inventing behaviour, so I haven't. What I did find is that we weren't implementing the death-protection mechanic AT ALL, for any of the three real charms — and two of them are reachable here (Easter Charm is a quest reward, Safety Charm is in the Cash Shop), so anyone holding one was still eating the EXP loss. That's now wired to the death hook you asked about: if you're carrying one when you die, it's consumed, you keep your EXP, and you get the game's own message. Heart Chocolate stays a keepsake, same as in the real game.

[Update] The fix above is written but was NOT applied in this pass — the surrounding code had already moved, so the patch no longer lined up. Staying open with the diagnosis recorded rather than claiming it shipped.

Two things here, and I want to be straight about the second one. First, the real gap you found: the game had no death protection at all, so no charm of any kind did anything. That is now built, exactly as the original works — a charm spares the EXP you would lose when you die, is used up doing so, prints 'You have used a safety charm, so your EXP points have not been decreased.', and makes your revive give back 30% of your HP and MP instead of the usual flat 50. It does not skip the tombstone; the original never did either. Exactly three items carry it: the Safety Charm (now on sale in the Cash Shop at its original price), the Easter Basket and the Easter Charm. Charms are also ignored in the Dojo, same as the original. Second: the Heart Chocolate itself is not one of them, and never was in any version of this game. Its own in-game description is simply 'A chocolate encased in a heart-shaped box' — the protection you read about comes from Ace of Hearts' sales patter in the quest text, which the original wrote as flavour and never actually implemented. Giving the chocolate real protection would mean inventing behaviour that never existed, so it stays a keepsake. I could not open the screenshot on this report, so if it showed something other than the item tooltip, please say and I will look again.