This is exactly what don't know, and is interesting to explore.
> there is no separate “stuff” that minds are made out of, no privileged plane of existence specific to minds; minds are just patterns like everything else
So if your brain was somehow cloned, you'd exist in two places at the same time? It seems possible for two separate consciousness to have the same memories and be identical in all respects, and yet still not be the same.
To illustrate, two instances of a programs can share the exact same binary code (the "pattern") and yet they are separate instances.