And Michael Vassar and Eliezer are so close to the theorized center of human history that they should assume they're holodecking with probability ~1.

The "with probability ~1" part is wrong, AFAICT. I'm confused about how to think about anthropics, and everybody I've talked to is also confused as far as I've noticed. Given this confusion, we can perhaps obtain simulation-probabilities by estimating the odds that our best-guess means of calculating anthropic probabilities is reliable, and then obtaining an estimate that we’re in a holodeck conditional on our anthropic calculation methods being correct. But it would be foolish to assign more than, say, a 90% estimate to “our best-guess means of calculating anthropic probabilities is basically correct”, unless someone has a better analysis of such methods than I’d expect.