It's risky business inferring personality from writing samples because people can and do adopt different styles in their writing depending on circumstance and whimsy. As an exercise, read something from James Mickens, and try to imitate his style for some other technical topic. It's actually not that hard, at least to get within throwing distance, refinement is always possible. He probably doesn't write family letters or most emails or technical documentation that way though. Once you have a broader sample from an author across different topics and genres, and even sampling on short-form writing or interviews, you can be on better footing for guessing what their personality is like without having to go through the effort of
getting to know them as an individual (which is otherwise the usual constraint) but you still risk being quite over-confidently wrong.
Certainly you're right that aspects of writing including style come to be expected over time by an audience, and if what were supposedly fixed things suddenly change it's usually not pleasant. Though to a fresh reader, the new version might be far preferable. Some authors could use an editor, some authors could tell their editor to back off more.
In the similar space of personalities we're discussing, I'd also bring up patio11, whose writing I've sampled for a long time here and elsewhere (I still think of him as the bingo card guy). I've mostly enjoyed it but I would not mind at all if his question-anticipating style and stating-things-precisely-but-also-precisely-vaguely-so-as-not-to-create-any-chance-at-liabilities style went away. The content overcomes the style and matters more, which I'd like to think is usual for me and how I evaluate things anyway.
The misanthrope comment is pretty funny. I'd disagree, especially considering how gwern has handled crazy person emails, but also because I'm somewhat misanthropic myself and figure gwern is probably less so, but who knows, it's a pretty bold thing to claim of someone else you don't know personally one way or another. I think what might be there for people to pick up on is a sense of superiority but in the form of distance, illustrated by this anonymous quote: "If I am superior to others, if I am above others, then I do not need others. When I say that I am above others, it does not mean that I feel better than them, it means that I am at a distance from them, a safe distance." (But again perhaps not, I just like that quote and is how I've felt of myself at times, more when I was younger.)
The opposite of orthogonal is non-orthogonal, the components are not completely independent, but it's left unstated how dependent they then are. (You could also say the inner product is non-zero if talking about vectors. There are many numbers that are non-zero.) I'd agree that there is something of an artist in an artist's works, but it's again risky (if you care about not being wrong too much anyway, or whatever consequences can come from being wrong) to speculate what exactly that something is, especially if all you have is the work. People all too often read way more into things than what is actually there. The author themself is a more reliable source for what parts of themselves are in something. (I'm reminded of Tolkien's hatred of allegory that he talks about in the preface. His letters go into further detail about what of the artist is or is not in art, intentionally or unintentionally. You could say the art itself talks about it too -- e.g. the Ring by nature of its maker is not like other mere tools which can be used for either good or evil.) For your first footnote, then, I'm in the camp of separation, and it's perfectly fine to talk of one without talk of the other, and for little of an artist's being to leak through. It's also healthier, at least I think it's unhealthy how many people seem to work themselves into a frenzy about something about the artist that prevents them from looking at the art more on its own. And again, if you're not using outside sources, what you can infer about someone purely from the art, purely from the fact that they made something rather than nothing, and this particular something rather than something else, is more limited than what some people imagine. "The Ass Goblins of Auschwitz" is a work of bizarro-fiction, I think there are plenty of people who would wish the author were killed just for admitting to having such thoughts by fact of putting them to paper. I don't actually know anything about the author, if there was any blurb about him in the book I've forgotten it over the actual book, but in any case I'd bet he's a fine guy in day to day life and not deserving of any trouble. (I am rather certain it's a he, though I don't recall his name.)
I also think it's fine to talk of the art and artist together, but it's not necessary, and usually less interesting, fruitful, or certain. But a sometimes-fun exercise in some fiction analysis can be: find the author's self-insert character. (That presupposes there is one, there sometimes isn't.) How sure are you that you've got it right? You should probably consult some information about the author themselves outside the art itself. And even then, is it a "complete insert", or a partial one, or one made of past regrets or future ideals or alternative paths, but not present bits?
While we're tossing light criticism about other people around in public, or as I'd put it just sharing opinions and viewpoints (this is not structured enough to be criticism), what comes to mind first for the three writers brought up is this: Maciej is funny even when he's wrong, pg is just insufferable when wrong, gwern is rarely wrong. I liked pg's older writing more, at some point he fell off and neither his tweets that occasionally surface to me nor his newer essays that I've bothered to read (last one I believe was "Good Writing") have left much of an impact or held my interest content-wise or style-wise. I haven't kept up with Maciej in tweet or other form since 2017 or so because I thought his content and style were repetitive and became boring (and wrong about things in ways that didn't invite counter argument or correction). My exposure to gwern's writing was IRC and LW comments from many years back, I've only read a fraction of his longer form work on his site but occasionally I'll read new things he puts out because he's still occasionally writing about new and interesting things. His style has never put me off, but sure, it's not routinely funny like I remember Maciej, and it lacks some sharpness and brevity that old-pg had. I still think it has personality, and a particular gwern-like personality even when it's in "classic style" mode that is shared by many other writers, but that might just be familiarity especially with his shorter form words.
And I still find gwern funny at times. This bit of fiction, for instance, has some amusing bits: https://gwern.net/fiction/clippy I wonder, does it satisfy your query of something as intriguing as "Empires Without Farms: The Case of Venice"? There are several ways that link can "make me care", though the web page layout can make it awkward. Is it the "clippy" in the URL, the official title "It Looks Like You’re Trying To Take Over The World", the one-sentence summary that just tells you it's a fictional short story about something, the two-sentence summary below that which says the same with a tiny bit more detail, the picture of Clippy, or the first lines of the actual text: "In A.D. 20XX. Work was beginning. “How are you gentlemen !!”… (Work. Work never changes; work is always hell.)"? Those first lines are distinctive video game references that even if one hasn't played the games, if one has been on the internet enough during a particular time then they'll likely ring a bell. The recognition of such signals is going to either act like crack ("One of us!") and draw the reader further in, or act as a repellent (quirk chungus) and bring forth a groan if not abandonment; I've been both kinds of reader for the same references. Meanwhile others won't get the references at all, it's just weird. Whether including such references indicates something meaningful about the author's personality directly, rather than just them being aware of the shibboleths and making use of them to attract and entertain a certain audience, is hard to say. Fans often end up with "don't meet your heroes" kinds of feelings when they over-empathized with their inferred construction of someone and thought they were part of the tribe rather than just making use of the tribe's signals.