My issue is with the jumping off a cliff scenario. I don't like the whole the DM determines if the PC jumped "for the right reasons," and if he doesn't think so - auto dead.
If the DM doesn't like the falling rules - ok, make them more lethal.
If the DM doesn't like the player's behavior (feels, probably justifiably, that's it's disruptive or irritating) - ok talk to the player about the behavior and resolve it.
But to have to adjudicate if the PC jumped "for the right reasons," just seems unnecessary when the rules have a clear outcome.
Note, the DM can do what he likes, I (IMO) don't think, in this case, they should - I think there are better resolution mechanisms here.
This is, unfortunately, a red herring that is often brought up. And by that, I mean, "Well, I see your point, but I don't want the DM judging why a player is doing something! Sure, we all might know it's ridiculous, but we can't let a DM determine if a player is doing things for the right reasons- what about player agency?"
Which is why, for the third time, I will use the old saying- even a dog knows the difference between kicked and stepped on. The fundamental precept of most tables is that everyone is working in
good faith, but good faith is not something that has some sort of objective rule or standard that we use.
We have human DMs in TTRPGs for a reason; this is not a simple mechanical application of rules. Just as a player has the right and the expectation that the DM will adjudicate fairly and in good faith, so too does the DM have the same right and expectation regarding the players; and, of course, the other players have the same expectations with regard to each other.
Look at the evolution of this concept. First, you have the idea of the "Bag o' rats." Of course, that is such a despised trope by many .... that the player attempting to skirt the rules comes up with a new one. "It's not a bag of rats; it's a ritualized chicken sacrifice! Because, you know,
Cthulhu I mean the Great Old Ones demands a chicken sacrifice every day for roleplaying reasons; it makes total sense and it's not something I came up purely for mechanical reasons. I probably read it in
The Colour out of Space. "
But if you think about it for even a second, it devolves quickly. Because this interpretation doesn't make sense. First, of course, you'd have to bring, care for, and transport a whole menagerie of chickens with you everywhere you go. But more importantly, it depends on the fact that there is no definition of creature, so you're looking for a loophole. I mean, it's clear from the context of the PHB that a "creature" almost always refers to a monster in a combat situation ("Sometimes, a DM might may out a map and use tokens or miniature figures to represent each creature involced in a scene" "Over the course of their adventures, the characters are confronted by a variety of creatures, objects, and situations" "Sometimes the adventurers and other creatures do their best to kill or capture each other in combat" "Combat, the focus of chapter 9, involves characters and other creatures swinging weapons, casting spells, maneuvering for position, and so on-all in an effort to defeat their opponents" and so on). Look at almost any ability- halflings, dragonborn breath, everything is about creatures. And look at spells- creatures everywhere.
But in fairness, not always! Look at gnomes- they can speak with small beasts and keep "creatures" like moles as their beloved pets. So what we know is that creature is just a general term that they use- even turn undead, after saying it is against undead, then says "A turned creature ..." What, a turned chicken?
But imagine if the DM starts to rules lawyer against you. We already saw sleep used; but that is the generic term used everywhere. So what if the DM demands that everytime we see "creature" that unless it specifies that you get to choose, we have to exhustively catalog the creatures (from bugs on up) in the area. It's not fun, is it? Because we don't want the DM to do that; it's taking rules literalism and making the game less fun for everyone; it's trying to take language that might be unclear and leveraging it.
So if you don't want the DM to behave like a jerk, don't let players do it either. If a player thinks Hex should be "always on," then discuss having that be a class feature with the DM. Don't demand cheesy interpretations.
And it's the same with the falling. Those people that say that these rules somehow "describe" the world; in my opinion, they are wrong. The rules just allow us to play a game. They are not perfect. The world doesn't suddenly change when errata gets released.
I agree that this is really about expectations and communications, and that they should match. But players know when a DM is being a jerk, and DMs (and players) know when a player is is as well.