Somehow I missed this post earlier. Well, not "somehow", I was on my phone. There are some good observations/questions here:
By "binding" I mean that once the dice are invoked the roll determines the result and that result is binding on all involved, meaning neither player nor DM can in good faith ignore it; in other words the generally accepted way of doing things since about forever.
This I agree with.
So, for example, the player says, "I want to try to persuade their highness to let me marry their heir." (Like how I avoided genders with that?)
The DM says, "Ok, I don't think they're going to go for that, from a penniless adventurer, so the DC is 30. And if you fail they are going to be offended and angry, so you could be in trouble. But, if you want to, go for it."
If the player rolls and succeeds, I would expect the DM to follow through. And if the roll fails, I would expect the player to not object to the consequences that were explained (if vaguely).
But...let's look what happens when it's NPC acting on PC:
DM: "Their highness is going to try to persuade you to marry their butler. I think you're probably desperate for a spouse right now, so I'm going to set the DC at 15. Here goes..."
Is it still "binding" if the player didn't actually agree to anything, or even declare an action that would get resolved by a roll? If it's just imposed on them by DM fiat?
EDIT:
I would agree with an argument that the player is bound by all the defined rules in the game: when you get hit with a sword, you lose hit points. When a dragon looks at you cross-ways you make a Wisdom roll, and if you fail you are Frightened. When a monster Shoves you, you get to make a contested Strength(Athletics) roll, and if you lose they pick whether you are Prone or moved. Etc. etc. etc. By playing the game, you are agreeing to be bound by the rules of the game.
But does that extend to whatever undefined consequences the DM improvises? Such as NPCs trying to persuade/intimidate/seduce you?