You were right when you said that the authors of "personal games" would probably take you the wrong way... It's hard not to. It's impossible to divorce the politics from the forms of these games, which, yes, makes them difficult to critique as formal designed objects without appearing to attack their politics.
These authors argue that "apolitical formalism" is inherently political, that the worst politics pretends it's not politics. Porpentine tweeted that she prefers "blatant bullshit over honeyed poison." (Uh, she was talking about you, by the way!)
I'm sure you'll understand these authors' reluctance to trust this kind of criticism after the past decade of sustained critical attack on such games and their contexts -- perhaps these "crimes" weren't always inflicted by you or whatever, but it's certainly a trigger when you begin your letter with wondering, "what is a game?" My brain shifts into red alert. That line of inquiry has been a long favored tool of well-intentioned oppression, because these arguments often masquerade as thoughtful discourse but function as a weapon of de-legitimization, that argue these personal games can't really fit a formal definition of game. The emotional leap is that these people can't really fit a formal definition of people. Adding, "it's okay if it's not a game" comes off as sounding like, "it's okay if you're not a person," which doesn't really help you seem apolitical.
Again, you're aware of this. You are a very carefully written letter.
I do think that you imply that this inability to separate content from form is an inherent (formal) weakness of personal games and the ways they mean things. That, because these games can't fit into a formalist frame, they are thus less game-like. Instead, I'd argue that this is a weakness of a traditional formalist approach: mechanics are often boring / limit what authors can do with games. (I'm construing your use of "agency" and "game-yness" as meaning "mechanics", because that's how I think you're actually using those concepts.)
I also think your idea of "dialogue" is too formalist. It emphasizes the shape of dialogue and presumes a positive effect, when I know better. In general, "promoting dialogue" is usually code for "we're going to go through the motions of a reasoned process, but we won't actually do shit." "Dialogue", on an oppressor's terms, rarely results in empathy. Outside of philosophy books, a dialectic is rarely fair and is subject to a power dynamic between the participants. (Poor Glaucon.) Fox News, for instance, often uses the "form" of dialogue to intimidate and mislead under the guise of being fair and balanced; and a few years ago, the completely rational dialectical democratic process of the state of California removed my right to marry. Dys4ia does not "argue with itself" because that'd compromise its politics -- it's taking its turn in the larger dialogue outside of the game, saying, "no, now YOU listen to ME for once."
I'm just trying to explain why authors of personal games don't / can't trust formalism... and now I notice what's happening: I'm rhetorically casting you in the role of Fox News, bigotry, and ignorance. See? You can't take the politics out of this!
There's simply no way to say, "Anna, you should've tightened up the graphics on level 3" without coming off like an asshole with an axe to grind. Maybe if we were talking about Starcraft, that nitpick could be legitimate critical dialogue and we could add it to the annals of Starcraft Studies and Starcraft theory because Starcraft is (partly) *about* the graphics on level 3, and "tight graphics" actually means something to the Starcraft developers. For personal games, it isn't and it never will be, partly because we are our games.
So here's what I propose: don't take this as, "these games think they're above formal criticism." Instead, perhaps formal criticism just occupies a space that's orthogonal / lateral / irrelevant to this game design space. We need a new mode of games criticism!
I mean, I do agree that formalism has its uses. Sometimes putting things into classes, categories, and types is useful. (Starcraft sure is interesting! Let's analyze all those systems!)
Unfortunately, here, I just don't think this is one of those situations.
Here, game design is not physics, engineering, or science -- rather, it's political science, it's history. Maybe we could approach our criticism of these games more like those fields?
I remain your most obedient servant,
-- Robert Yang