>Simulationism is predicated on the hypothesis that we could construct a completely accurate simulation of our universe in our universe, as if recursively-simulated universes are possible it becomes vanishingly unlikely that we do not live in one, so demonstrating that that's possible would be pretty important.

Actually it wouldn't have to be "a completely accurate simulation of our universe in our universe". A "somewhat accurate simulation of our universe in our universe" would also do for the statistical purposes of that premise. If you have recursively-simulated universes, even if they are not 100% like each other, it shouldn't change the probabilities, right?

That said, I don't fully agree with the main premise:

>if recursively-simulated universes are possible it becomes vanishingly unlikely that we do not live in one

Sounds to me somewhat akin to the faulty "ontological proof of the existence of God" ("Anselm defined God as "that than which nothing greater can be conceived", and then argued that this being could exist in the mind. He suggested that, if the greatest possible being exists in the mind, it must also exist in reality. If it only exists in the mind, a greater being is possible—one which exists in the mind and in reality.").