Assuming for a moment that Everett’s interpretation is correct, there will eventually be a way to very confidently deduce this (and time, identity and consciousness work pretty much like described by Drescher IIRC—there is no continuation of consciousness, just memories, and nothing meaningful separates your identity from your copies):
Should beings/societies/systems clever enough to figure this out (and with something like preferences or values) just seek to self-destruct if they find themselves in a sufficiently suboptimal branch, suffering or otherwise worse off than they plausibly could be? Committing to give up in case things go awry would lessen the impact of setbacks and increase the proportion of branches where everything is stellar, just due to good luck. Keep the best worlds, discard the rest, avoid a lot of hassle.
This is obviously not applicable to e.g. humanity as it is, where self-destruction on any level is inconvenient, if at all possible, and generally not a nice thing to do. But would it theoretically make sense for intelligences like this to develop, and maybe even have an overwhelming tendency to develop in the long term? What if this is one of the vast amount of branches where everyone in the observable universe pretty much failed to have a good enough time and a bright enough future and just offed themselves before interstellar travel etc., because a sufficiently advanced civilization sees it’s just not a big deal in an Everett multiverse?
(There’s probably a lot that I’ve missed here as I have no deep knowledge regarding the MWI, and my reading history so far only touches on this kind of stuff in general, but yay stupid questions thread.)
In general, vegetarians don’t care as much about e.g. species flourishing as they do about the vast amounts of suffering that farmed animals are quite likely to experience. I see nothing strange in viewing animals as morally relevant and deeming their life a net negative, thus hoping they wouldn’t have to exist.
Eating only free range or hunted meat is a pretty good option, although of course not entirely unproblematic, from the suffering-reduction point of view. It is very often brought up by non-vegetarians whenever the topic of animal suffering comes up—anecdotally I counted four people I know who I have heard using the argument when explaining or defending their meat eating. None of them actually even eats mainly free range or hunted meat. To me, it seems the whole point is unfortunately only ever used as a motte that people retreat to to avoid having to feel or look bad, before again just eating whatever as soon as they can stop thinking about it. This might not mean these people don’t really care on some level: I’d guess it is more expensive cognitively to analyze and keep tabs on which meat products cause only acceptable amounts of suffering, without succumbing to rationalization and constant habit-breaking and eventually forgetting the project, than it is to just rule meat out of your diet and stop thinking about it.
Another reason why free-range and hunted meat are not quite equivalent to veg(etari)anism is that they don’t seem to scale as easily to feed large populations for a reasonable land area and product price. That said, I for one would welcome a society which mostly eats plant-based food, but with the very occasional expensive hunted or ethically-farmed piece of meat or cheese, which indeed seems like what a non-factory-farming omnivore society could end up looking like. (Of course, for us embracing a more negative form of utilitarianism, wild-animal suffering would still be a problem, but that’s beyond the scope of this discussion.)