Nitpicking; I meant that falsifiability-in-practice-as-such-the-way-most-people-use-the-word is not a necessary precondition for determining which hypotheses to pay attention to. Apparently unfalsifiable hypotheses (which are nonetheless probably actually falsifiable with enough computing power) like the existence of a creator God are thus fair game for Bayesians, and pointing out their apparent unfalsifiability isn't scoring a point for the atheists.

Wrong. A consequence of Bayes' Theorem is that if two theories A and B fit the data equally well, but A fits hypothetical alternative data better than B does (in other words, B is more falsifiable) then A must assign a lower conditional probability to the actual data than B, by conservation of probability. This means that regardless of where the priors start out, if we keep accumulating evidence without falsifying either the probability of A must eventually become vanishingly small, too small for any reasonable person to even spare the time to consider the hypothesis.

I don't know what an ontologically fundamental state would look like (when I think of people who believe in the supernatural that does not seem to describe their beliefs at all)

Believing in ontologically fundamental mental states means the you believe that the actual territory, as opposed to a map, contains minds. This can seem reasonable, but the reasonableness is an illusion caused by the fact that our monkey brains are pretty good at thinking about other monkey brains and pretty bad at thinking about much simpler things, such as maths.

God falls into this category as normally postulated, since he is usually assumed to be fundamental and is usually assigned mental states as well as exhibiting the complex behaviour typical of minds. Ghosts fall into it since for a person's mind to survive the destruction of the physical entity it was contained in/supervenient upon it must have its own ontologically fundamental properties.

Here's a basic argument for a somewhat vague Creator God: the universe exists. Things that exist tend to have causes. Powerful things like superintelligences or transcendent uploads are good at causing things. This universe might have been caused by one of those really powerful things.

Here's the corresponding argument for ghosts: death is an event. People's conciousness tends to continue existing through most events, so it probably continues existing through death even though it has never been observed to do so (the same way no universe has been observed to have a cause). Therefore minds must continue existing after death, and we might as well call them ghosts.

Motivated cognition at its worst.

That we feel better when we call those powerful things 'superintelligences' instead of 'gods' just says something about our choice of ontology, not about the righteousness of our epistemology.

No, it shows that we are cautious that the connotations of our statements don't say anything that we don't mean.