Actually, I'm just interested. I've been wondering if big world immortality is a subject that would make people a) think that the speaker is nuts, b) freak out and possibly go nuts or c) go nuts because they think the speaker is crazy; and whether or not it's a bad idea to bring it up.

Are people close to you aware that this is a reason that you advocate cryonics?

What cosmological assumptions? Assumptions related to identity, perhaps, as discussed here. But it seems to me that MWI essentially guarantees that for every observer-moment, there will always exist a "subsequent" one, and the same seems to apply to all levels of a Tegmark multiverse.

(I'm not convinced that the universe is large enough for patternism to actually imply subjective immortality.)

Why wouldn't it be? That conclusion follows logically from many physical theories that are currently taken quite seriously.

I'm not willing to decipher your second question because this theme bothers me enough as it is, but I'll just say that I'm amazed figuring this stuff out is not considered a higher priority by rationalists. If at some point someone can definitely tell me what to think about this, I'd be glad about it.

I guess we've had this discussion before, but: the difference between patternism and your version of subjective mortality is that in your version we nevertheless should not expect to exist indefinitely.

I feel like it's rather obvious that this is approximately what is meant. The people who talk of democratizing AI are, mostly, not speaking about superintelligence or do not see it as a threat (with the exception of Elon Musk, maybe).

You also can't know if you're in a simulation, a Big quantum world, a big cosmological world, or if you're a reincarnation

But you can make estimates of the probabilities (EY's estimate of the big quantum world part, for example, is very close to 1).

So really I just go with my gut and try to generally make decisions that I probably won't think are stupid later given my current state of knowledge.

That just sounds pretty difficult, as my estimate of whether a decision is stupid or not may depend hugely on the assumptions I make about the world. In some cases, the decision that would be not-stupid in a big world scenario could be the complete opposite of what would make sense in a non-big world situation.

If you're looking for what these probabilities tell us about the underlying "reality"

I am. It seems to me that if quantum mechanics is about probabilities, then those probabilities have to be about something: essentially, this seems to suggest that either the underlying reality is unknown, indicating that quantum mechanics needs to be modified somehow, or that Qbism is more like an "interpretation of MWI", where one chooses to only care about the one world she finds herself in.

Fortunately, Native American populations didn't plummet because they were intentionally killed, they mostly did so because of diseases brought by Europeans.