Attempts to analyze good instadeaths versus bad instadeaths (loosely defined as ones that are instant hard-to-avoid deaths that aren’t really similar to running out of HP):

• Poison, digestion, lava, death magic, and drawbridge instadeaths can easily be converted into HP damage of max(damage dice roll, substantial % of your max HP).
• Drowning and choking would be well-suited to a breath system, where it becomes a delayed instadeath. Especially so if you can stop the clock by putting on an amulet of magical breathing or praying.
• Intelligence drain and level drain generally can’t happen without the player being given ample time to escape, so they are fine.
• Starvation could be changed to HP loss, but you usually just die from side effects of fainting anyway.
• Instadeaths that almost always have to be intentionally caused by the player (self-genocide, divine wrath etc) are generally fine as-is.
• Instakilling artifacts are problematic, because there is currently no recourse except for the amulet of life saving.
• Eating or digesting the Riders should not instakill without warning, because it is now unexpectedly a bad idea to eat a reviving corpse, whereas it had been a good idea in the rest of the game.
• Good instadeaths generally use unusual resources to fix, or hit the player’s reserves in an unexpected way, and allow the player a chance to get out or stop it before dying.