I agree with criticism for 2 assumption. Although I have this intuition (based on possibly very wrong intuitions I have about QM), that argument still works even without it: Imagine same human runs the simulation. Then he goes to another table where he runs spin measuring experiment, with 50/50 probability of getting either up or down. After seeing the result, there is now two different consciousness of him, but there is still just one copy of simulated brains as they did not saw the result.
Lets assume few things:
1. Many Worlds is real.
2. All identical consciousnesses measures as 1 in anthropics . So if we have set of consciousness: 1xA,1xB and 1000000xC, it is still 1/3 chance, to perceive being C.
Now say some intelligent being (i.e. human) starts another human brain simulation on silicon chip. The operations it does are all discrete, so despite the chip splitting in to many chips in many worlds, the simulated consciousness itself remain just 1 (because of #2 assumption).
But that is not true for human who started the simulation as he differs somehow in every Everett branch and reaches billions different consciousnesses really fast.
Is there some mistake in reasoning, that real persons should heavily outweigh simulations, despite, how many of them are running, given such assumptions?