There might be a confusion. Did you get the impression from my post that I think MIRI was trying to solve philosophy?

I do think other MIRI researchers and I would think of the MIRI problems as philosophical in nature even if they're different from the usual ones, because they're more relevant and worth paying attention to, given the mission and so on, and because (MIRI believes) they carve philosophical reality at the joints better than the conventional ones.

Whether it's "for the sake of solving philosophical problems or not"... clearly they think they would need to solve a lot of them to do FAI.

EDIT: for more on MIRI philosophy, see deconfusion, free will solution.

It appears Eliezer thinks executable philosophy addresses most philosophical issues worth pursuing:

Most “philosophical issues” worth pursuing can and should be rephrased as subquestions of some primary question about how to design an Artificial Intelligence, even as a matter of philosophy qua philosophy.

"Solving philosophy" is a grander marketing slogan that I don't think was used, but, clearly, executable philosophy is a philosophically ambitious project.

None of what you're talking about is particular to the Sequences. It's a particular synthesis of ideas including reductionism, Bayesianism, VNM, etc. I'm not really sure why the Sequences would be important under your view except as a popularization of pre-existing concepts.

Decision theory itself is relatively narrowly scoped, but application of decision theory is broadly scoped, as it could be applied to practically any decision. Executable philosophy and the Sequences include further aspects beyond decision theory.

No because it's a physics theory. It is a descriptive theory of physical laws applying to matter and so on. It is not even a theory of how to do science. It is limited to one domain, and not expandable to other domains.

...try reading the linked "Executable Philosophy" Arbital page?

Seems like a general issue with Bayesian probabilities? Like, I'm making a argument at >1000:1 odds ratio, it's not meant to be 100%.

I see why branch splitting would lead to being towards end of universe, but the hypothesis keeps getting strong evidence against it as life goes on. There might be something more like the same number of "branches" running at all times (not sharing computation), plus Bostrom's idea of duplication increasing anthropic measure.

Yes

This gets into philosophy about reference machines in general. You don't want to make a relativist argument that is too general, because then you could say "my niche physics theory is very simple relative to a reference machine for it, it just looks complicated to you because you are using a different reference machine". With priors I'm looking for a thing that could be figured out without looking at the empirical world. Humans figured out lots of math, including classical computation, before figuring out the math of quantum computation. This is despite living in a quantum world. Quantum mechanics has a reputation for being unintuitive, even though we live in a quantum universe it is descriptively true that human natural prior-like complexity measures encoded in the brain don't find quantum mechanics or quantum computation simple.