"Mind" is a high level concept, on a base level it is just a subset of specific physical structures. The precise arrangement of water molecules in a waterfall, over time, matches if not dwarves the KC of a mind.

That is, if you wanted to recreate precisely this or that waterfall as it precisely happened (with the orientation of each water molecule preserved with high fidelity), the strict computational complexity would be way higher than for a comparatively more ordered and static mind.

The data doesn't care what importance you ascribe to it. It's not as if, say, "power", automatically comes with "hard to describe computationally". On the contrary, allowing for a function to do arbitrary code changes is easier to implement that defining precise power limitations (see constraining an AI's utility function).

Then there's the sheer number of mind-phenomena, are you suggesting adding one by necessity increases complexity? In fact, removing one can increase it as well: If I were to describe a reality in which ceteris is paribus, with the exception of your mind not actually being a mind, then by removing a mind I would have increased overall complexity. Not even taking into account that there are plenty of mind-templates around already (implicitly, since KC, even though uncomputable, is optimal), and that for complexity considerations, adding another of a template isn't even adding much, necessarily (I'm aware that adding just a few bits already comes with a steep penalty, this comment isn't meant to be exhaustive). See also the alphabet example further on.

Then there's the illusion that somehow our universe is of low complexity just because the physical laws governing the transition between time-steps are simple. That is mistaken. If we just look at the laws, and start with a big bang that is not precisely informationally described, we get a multiverse host of possible universes with our universe not in the beginning, which goes counter the KC demands. You may say "I don't care, as long as our universe is somewhere in the output, that's fine". But then I propose an even simpler theory of everything: Output a long enough sequence of Pi, and you eventually get our universe somewhere down the line as well. So our universe's actual complexity is enourmous, down to atoms in a stone on a hill on some moon somewhere in the next galaxy. There exists a clear trade-off between explanatory power and conciseness. I used to link an old Hutter lecture on that latter topic a few years ago, I can dig it out if you'd like. (ETA: See for example the paragraph labeled "A" on page 6 in this paper of his).

The old argument that |"universe + mind"| > |"universe"| is simplistic and ill-applied. Unlike with probabilities, the sequence ABCDABCDABCDABCD can be less complex than ABCDABCDABCDABC.

The list goes on, if you want to focus on some aspect of it we can go into greater depth on that. Bottom line is, if there's a slam dunk case, I don't see it.

his is very different from following wherever someone would have their feelings hurt if you didn't go.

What did you have in mind specifically?

Of course, rationality also involves the use of priors, evidence, and accumulated information over your entire lifetime.

Rationality also involves paradigm shifts, revolutions and inversions. "Use priors" is not, should not be, a call for fundamental conservatism.

You are not merely allowed but required to assign a very low prior, in the range of "bloody ridiculous", to propositions which contradict all your available information, or require some massively complex rationalization to be compatible with all your available information.

One person's complex rationalisation is another's paradigm shift.

Evolution, relativity and quantum physics are paradigm shifts. Some people still aren't aboard with some of them, finding them against "logic", "reason", "common sense", etc. The self-professed rationalist Ayn Rand rejected all three: do you want to be another Ayn Rand?

The conservative incremental paradigm, applied retroactivley, would lead lwrationalists to reject good science. So they kind of don't believe in it as the only paradigm. But they also kind of do, since it is the only paradigm they use when discussing theology., or other things they don't like.