Replying out of order because it's how my thoughts happened.
Ironsworn basically compels the GM at times to openly and truthfully, with the assent of the players, re-write certain elements of the fiction. How does this break trust?
It doesn't. Because you did it in the open.
I specifically referred to this being done
secretly, not "openly and truthfully". Things done in the open can be addressed if people have a problem with how they were done--and if the players really do have a problem, I don't think they'll assent!
You have generalized what I said into something I didn't say, and thus taken umbrage with the thing I didn't say. I was
very specifically referring to things done secretly, things done in ways the players could not ever know or see. Because that's what people were talking about. Repeatedly. Things like the party having meaningful evidence that
was factual, up until the moment a move happened that made it okay to make it
not factual. That's the kind of thing which disconnects the process that the players could use to reason.
Even if the rules and procedures sanction the GM to declare a new fact which establishes that the Countess was the killer rather than the Earl, the fact that it
was not established until that fact was declared means the players couldn't be
reasoning toward that conclusion--as, very literally, there was nothing to reason toward until that declaration occurred. This isn't fudging, but it does break the chain of player reasoning; everything they have previously observed remains in a superpositional limbo between "valid clue pointing to the real result" and "false lead trying to prevent you from finding the real result", and both results are perfectly consistent with the fiction of a whodunnit situation. When both results are perfectly consistent with the fiction but mutually exclusive and (usually) jointly exhaustive, it becomes impossible to do any reasoning with them. Everything reduces to conditionals, and the thing which resolves that conditional is...establishing whatever was unknown, thus ending the mystery via that establishment, rather than ending the mystery by connecting the proverbial dots.
And intent matters in these situations. Greatly. And certainly there are degrees to it that matter greatly as well.
Certainly. Hence why I specifically talked about doing it
secretly. I even used that word: "secretly rewrite"!
Sure, no problem. I do think there was an exceptionally salient point made earlier by @deleuzian_kernel that the only thing creating an "objective mystery" does from a long-term gameplay state is create some "meta" externality status that the players can use as a "badge of honor" for their cleverness. As they note, this is purely aesthetic---it "feels" right to do it that way to achieve a certain sort of gameplay reward for the participants.
I think this is needlessly dismissive, which is a bit frustrating considering you've portrayed
me as being needlessly dismissive of something I haven't actually dismissed at all and have specifically and repeatedly said is 100% fine. Specifically, this "badge of honor" analysis trivializes the player experience into nothing more than bragging rights, which has nothing to do with the goal in question. In
Ironsworn (which, believe it or not, I have actually played!) is about giving players the personal experience of being in an early Iron Age society where vows and mighty deeds (and the attendant risk of extreme failure and difficult stuff) are core to your life, when I play or run a "whodunnit" adventure, I want to have (as a player) or produce (as the GM) the personal experience of mystery-solving, of "epiphany" if you'll permit my poetic license.
That is, there is value in the feeling of epiphany, of the personal experience of realizing what all these little facts were building up to all along. Indeed, that feeling of epiphany in an educational context is one of my favorite experiences of all, second only to
seeing it in another's eyes as I help guide them through something they don't understand yet. (There's a shift in a person's eyes, it's subtle but distinctive, as the pieces fall into place and suddenly the mind is opened to a new perspective.) I don't think this has anything to do with a "badge of honor" effect. Instead, it is an internal feeling of gaining understanding, which is a neat feeling.
Doing it with a different aesthetic in mind---creating and provoking thematic consequences and hard choices---creates a different sort of decision space for what makes the "mystery" of interest in the first place.
Sure. Would you like me to dig up the multiple places where I specifically said there's nothing wrong with that, it just doesn't do the specific thing I'm wanting a "whodunnit" experience to do and thus
for what I want it causes problems? Because I did say that. Several times. I repeatedly said there's nothing wrong with a set of rules or procedures that produce the experience of "my character solves mysteries" without producing the experience of "I, personally, am solving mysteries". It would be incredibly foolish for me to claim otherwise, since the vast majority of experiences you can have via TTRPGs are ones where you
personally cannot experience it, but your character can and maybe even must.