I agree with vallinder's point, and would also like to add that arguments for moral realism which aren't theistic or contractarian in nature typically appeal to moral intuitions. Thus, instead of providing positive arguments for realism, they at best merely show that arguments for the unreliability of realists' intuitions are unsound. (For example, IIRC, Russ Shafer-Landau in this book tries to use a parity argument between moral and logical intuitions, so that arguments against the former would have to also apply to the latter.) But clearly this is an essentially defensive maneuver which poses no threat to the orthogonality thesis (even if motivational judgment internalism is true), because the latter works just as well when you substitute "moral intuition" for "goal."

If I scratch my nose, that action has no truth value. No color either.

The proposition "I scratched my nose" does have a truth value.

See the distinction. Don't hand wave it with "it's all the same", "that's just semantics", etc. You started saying that this is more of a question. I've tried to clarify the answer to you.

Do you know Jon Williamson's work? It seems to give an answer to your question (but I've not read it yet). Here's the first paragraph of Section 9.1 “Mental yet Objective” of his book “Bayesian Nets and Causality”:

Epistemic causality embodies the following position. The causal relation is mental rather than physical: a causal structure is part of an agent’s representation of the world, just as a belief function is, and causal claims do not directly supervene on mind-independent features of the world. But causality is objective rather than subjective: some causal structures are more warranted than others on the basis of the agent’s background knowledge, so if two people disagree about what causes what, one may be right and the other wrong. Thus epistemic causality sits between a wholly subjective mental account and a physical account of causality, just as objective Bayesianism sits between strict subjectivism and physical probability.

Here's a link to his papers on causality. At least the fifth, “Causality”, contains an introduction to epistemic causality.

There may be an objectively correct way to throw globs of paint at the wall if I wish to do it in a way that is consistent with certain desired properties given my state of knowledge. That would not make that correct way of throwing globs of paint "true".

A la Jaynes, there is a correct way to assign degrees of belief based on your state of knowledge if you want your degrees of belief to be consistent with certain constraints, but that doesn't make any particular probability assignment "true". Probability assignments don't have truth value, they assign degrees of belief to propositions that do have truth value. It is a category error, under Jaynes perspective, to assert that a probability assignment is "true", or purple, or hairy, or smelly.

I was pointing out that your original statement characterizing "most people here" as asserting that "probability claims are true ..." is antithetical to Jaynes's approach, which I take as the canonical, if not universal, view on this list.

1. Probability is "in the mind," i.e., probability claims are true only in relation to some prior distribution and set of information to be conditionalized on;

That statement is too imprecise to capture Jaynes's view of probability. He demonstrates (YMMV) that there is a unique way to assign probability to represent your degree of belief in propositions in a way that is consistent with certain desired properties of degrees of belief. That doesn't make the probability assignment "true", it just makes it consistent with your knowledge and the desired properties. IN particular, it won't make the probability distribution you assign match some ill defined long term frequency of some event occurring.

I don't understand where the tension is supposed to come in. The idea that causation is in the mind, not in the world is part of the Humean tradition and has been a respected (although minority) position in philosophy for centuries. If anything, it seems to mesh particularly well with empiricist leaning philosophies (especially those with an anti-metaphysical stance).

No considerations are given for the strength of the advantage

I wish this were stressed more often. It's really easy to think up selective pressures on any trait and really hard to pin down their magnitude. This means that most armchair EP explanations have very low prior probabilities by default, even if they seem intuitively reasonable.

The word "cult" never makes discussions like these easier. When people call LW cultish, they are mostly just expressing that they're creeped out by various aspects of the community - some perceived groupthink, say. Rather than trying to decide whether LW satisfies some normative definition of the word "cult," it may be more productive to simply inquire as to why these people are getting creeped out. (As other commenters have already been doing.)