In You Provably Can't Trust Yourself, Eliezer tried to figured out why his audience didn't understand his meta-ethics sequence even after they had followed him through philosophy of language and quantum physics. Meta-ethics is my specialty, and I can't figure out what Eliezer's meta-ethical position is. And at least at this point, professionals like Robin Hanson and Toby Ord couldn't figure it out, either.
Part of the problem is that because Eliezer has gotten little value from professional philosophy, he writes about morality in a highly idiosyncratic way, using terms that would require reading hundreds of posts to understand. I might understand Eliezer's meta-ethics better if he would just cough up his positions on standard meta-ethical debates like cognitivism, motivation, the sources of normativity, moral epistemology, and so on. Nick Beckstead recently told me he thinks Eliezer's meta-ethical views are similar to those of Michael Smith, but I'm not seeing it.
If you think you can help me (and others) understand Eliezer's meta-ethical theory, please leave a comment!
Update: This comment by Richard Chappell made sense of Eliezer's meta-ethics for me.
It was an explanation for why your thought experiment provides a bad motivation: we can just forbid modification of human brains to stop the thought experiment from getting through, but that would still leave a lot of problems, which shows that just this thought experiment is not sufficient motivation.
Sure, the superintelligence thought experiment is not the fully story.
One problem with the suggestion of writing a rule to not alter human brains comes in specifying how the machine is not allowed to alter human brains. I'm skeptical about our ability to specify that rule in a way that does not lead to disastrous consequences. After all, our brains are being modified all the time by the environment, by causes that are on a wide spectrum of 'direct' and 'indirect.'
Other problems with adding such a rule are given here.