It feels to me like so much of this discussion is predicated on a kind of bad faith relationship between the DM and players. But is that how we are actually playing? It's hard to imagine.
Like, I'm not trying to catch out my players, and I assume the same from them. If the player says "I smash the vase" I am always trying to go with how I perceive their intent, and the players understand that we are all on the same side. They'll correct me if I get something wrong, but I also don't see them trying to retcon if they made a mistake by not thinking through the situation. Unless it was kind of a dumb mistake that would have been obvious to character in the situation, and then they just correct it and I generally agree, figuring I could have done a better job on my description. But generally when a players screws up - often through impatience - they own it and we see where it goes. Same goes for the DM - I screw up with my NPCs all the time but c'est la vie.
Agreed in general, and I appreciate players who take this approach.
However, not all do; and I've seen more than enough attempted take-backs and retcons over time when things go unexpectedly wrong from what seemed like a simple action (a silly example here might be smashing a china vase without realizing it's full of nitroglicerine); and can do without those arguments. Thus, I put my foot down quickly.
And as a player...my screw-ups are usually more fun than what I should have done! Life is full of mistakes, and now the plot has a new wrinkle. My bone-headed maneuvers have given us more good memories than my genius ideas, that's for sure (partly because they are so much more numerous).
This is great, and I say that in a good way!
One classic example from my game of both the good and bad, from about 2001, went like this: party was in a methane-laden swamp, detailed as such in the canned module I was running. The swamp is something of a trap in that while there you meet a few trolls but lighting any sort of fire results in the methane going up as a full fireball. I had narrated that there was a distinct smell of methane or something similar and at least one player, in character, said something like "We'd better not light any fires here". So far so good; and these were four very intelligent players.
Then they met the trolls, and after killing them the party MU - without thinking - blithely cast
Flaming Sphere to toast the bodies. The following conversaton went like this:
Me: "OK, you cast you spell - you all need saving throws."
All four players in perfect unison, after a two-second silence: "D'oh!", followed by a roar of laughter.
Saves were failed all over the place, and a majestic meltdown of magic items followed. By the time the dust settled, of a party of about 8 (I forget the exact number) one character was dead, two others were barely alive, and over 100,000 g.p. worth of magic had gone up in smoke. And everyone was laughing....
...until the next week, when the player who had missed that session* showed up and started squawking, demanding retcons and do-overs because his character(s? I think he had two at the time) - while still alive - had lost some expensive gear. That was one long and nasty argument, and turned something everyone else had seen as a silly mistake and gloriously fun moment into a drawn-out ordeal. Soured the
Flaming Sphere's caster on the game for years.
* - it had long been established table policy at the time (and still is today) that if you-as-player miss a session your character(s) is(are) still in action, and left in the hands of others to play; which they will in good faith. Any pre-instructions given by the missing player to the DM and-or one or more other players are expected to be followed as closely as practical.
