799
(dnd 5e) Prove me wrong, RAW
(sh.itjust.works)
Disclaimer: this is purposefully obtuse.
Other effects in the game which explicitly state they kill you:
Shadows, succubi, massive damage, death saving throws, beholder death ray (notably not even their disintegration ray kills you), power word kill, vampires, mind flayers, night hags, drow inquisitors.
Clearly, if they intended for disintegration to kill you, they'd have said so. Since specific overrides general, and there is no general rule that disintegrated creatures are dead, I rest my case. QED.
If a guy is doing what you're doing in this thread at the table, then yeah, I'd support them in leaving you there.
Doing what? Trying to play by the rules? It's a game! Games have rules. If you can't accept someone living out their pile of dust fantasy, which is clearly supported by the rules, then I think you need to take a long look in the mirror and ask yourself who hurt you.
You are 100% free to live out your pile of dust fantasy. I let you be a pile of dust. Isn't that what you wanted?