The prior is that in a seemingly "99.9+% lizardman world" you are the lizardman. How would one tell the difference?
Ah, that's just a 1,000:1 odds ratio update. Strong evidence is common. It's quite straightforward to get the evidence that you are not a lizardman.
I just mean to say, in a world where the ratio of lizards (literally the animal) to humans is 1,000,000,000:1, you should very easily be able to find out which one you are, even though the prior is (let's say) that you are a lizard.
If a lizardman is one who is combative about an unpopular opinion which they hold, and the world is 99.9% lizardman, then that means that only 700 million people in the world are not combative about any of their unpopular views. I suppose that you could recognize that you're just a generally chilled out person who doesn't get into arguments or complain, and has a common-sense worldview that most people agree with. After all, lizardman doesn't have to have all unpopular views - just one that they're combative about. They could still be calm and conformist in most areas of life.
You could use things like being able to outperform the market, being consistently ahead of the Overton window, finding a reception for your less objectively verifiable ideas among (a small group of) other high-performing individuals. This doesn't guarantee that you're not still a lizardman among the 99.9%+ lizardmen, just in a high-performing contrarian cluster (hence my rule #1), but at least rules out being a crazy person living in a normal world (unless you're just hallucinating all of the evidence, but there's no point worrying about that).
Assuming "lizardman" here is referring to this post, the usage of terminology seems wrong. In that post, "lizardman" is used specifically to mean rare outliers, so under that definition, it's quite impossible for 99.9%+ of the world to be that. It also portrays a particular archetype of unreasonable person, which I think is what you're intending to refer to; but as far as I can tell that archetype is in fact rare.
That post made me write this post, but I'm not sure that I'm referring to the same thing. Basically I mean something like "people whose beliefs or actions are so unreasonable, even on things that they should have thought long and hard about, that they seem to belong to a different species from myself." Like Robin Hanson in this tweet or Elizer Yudkowsky when he thought he would singlehandedly solve all the philosophical problems associated with building a Friendly AI (looks like I can't avoid giving examples after all). I'm pretty sure these two belong in the top 0.1 percentile of all humans as far as being reasonable, hence the title.
For the record my update here has been of the sort "I should expect from the outside that I would also see this sort of behavior from myself without a very targeted effort to avoid it, as it seems to me like a human universal" rather than "This is an easy mistake for me to avoid".
I'm very curious what examples were deleted. even in a high threat world, there's strong evidence that rate of cooperate is not as bad as OP believes, but they're convinced otherwise. their post history focuses on stock trading and buying gold, and mentions Mitchell getting fired from Google. hard to infer anything specific from those, but very interesting.
How much does this thinking depend on the ratio being that extreme? Does it hold at 90%? 51%? What if most lizardmen are actually pretty OK on the majority of their actions, and only alien occasionally?
Actually, I think I need a bit more explanation of what you mean by "lizardman", and whether I should care about distant humans any more than I do distant lizardmen. If you changed the title to "99.9+ short-sighted and irrational humans", I think I could agree.
[Redacted a few paragraphs talking about why it seems like I'm living in a 99.9+% lizardman world. Unlikely to convince anyone who doesn't already think this, and will probably offend a bunch of people, such as the ones I used as examples.]