And yes, if one's own preferences are the foundation of ethics, most philosophers would simply call this subject matter practical rationality rather than morality.
They would be missing some important distinctions between what we think of as our moral values and what we think of as "chocolate/vanilla" preferences. For one obvious example, consider an alien ray gun that 'switches the way I feel' about two things, X and Y, without otherwise affecting my utility function or anything else of value to me.
If X were, say, licorice jelly beans (yum) and Y were, say, buttered popcorn jelly beans (yuck), then I wouldn't be too deeply bothered by the prospect of being zapped with this gun. (Same for sexual preference, etc.) But if X were "autonomy of individuals" and Y were "uniformity of individuals", I would flee screaming from the prospect of being messed with that way, and would take some extreme actions (if I knew I'd be zapped) to prevent my new preferences from having large effects in the world.
Now we can develop whole theories about what this kind of difference consists in, but it's at least relevant to the question of metaethics. In fact, I think that calling this wider class of volitions "preferences" is sneaking in an unfortunate connotation that they "shouldn't really matter then".
This sounds, to me, like it's just the distinction between terminal and instrumental values. I don't terminally value eating licorice jelly beans, I just like the way they taste and the feeling of pleasure they give me. If you switched the tastes of buttered popcorn jelly beans (yuck indeed) and licorice jelly beans, that would be fine by me. Hell, it would be an improvement since no one else likes that flavor (more for me!). The situation is NOT the same for "autonomy of individuals" and "uniformity of individuals" before I really do have terminal values for these things, apart from the way they make me feel.
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.