I read it as saying, "Suppose there is a mind with an anti-Occamian and anti-Laplacian prior. This mind believes that . . ." but of course saying "there is a possible mind in mind design space" is a much stronger statement than that, and I agree that it must be justified. I don't see how such a mind could possibly do anything that we consider mind-like, in practice.

Really, I don't know if this has been mentioned before, but formal systems and the experimental process were developed centuries ago to solve the very problems that you keep talking about (rationality, avoiding self deception, etc). Why do you keep trying to bring us back to 500 BC and the methods of the ancient greeks? Is it because you find actual math too difficult? Trust me, it's still easier to do math right than to do informal reasoning right. On the other hand, it's much more rewarding to do informal reasoning wrong than to do the math wrong. This may be the source of the problem.