And that's what morality always was in the first place. It's a way of getting other people to do otherwise than what they wanted to do. No one would be convinced by "I don't want you to kill people", but if you can convince someone that "It is wrong to kill people", then you've created conflict in that person's desires.

That's one of the things morality has been, and it could indeed be the main thing, but my point above is it all depends on what the person means. Even though getting other people to do something might be the main and most important role of moral language historically, it only invites confusion to overgeneralize here - though I know how tempting it is to simplify all this ethical nonsense floating around in one fell swoop. Some people do simply use "ought" to mean, "It is in your best interest to," without any desire to get the person to do something. Some people mean "God would disapprove," and maybe they really don't care if that makes you refrain from doing it or not, but they're just letting you know. These little counterexamples ruin the generalization, then we're back to square one.

I think the only way to really simplify ethics is to acknowledge that people mean all sorts of things by it, and let each person - if anyone cares - explain what they intended in each case.

No, scratch that. The reason ethics is so confused is precisely because people have tried to simplify a whole bunch of disparate-but-somewhat-interrelated notions into a single type of phrasing. A full explanation of everything that is called "ethics" would require examination of religion, politics, sociology, psychology, and much more.

For most things that we think we want ethics for, such as AI, instead of trying to figure out that complex of sundry notions shoehorned into the category of ethics, I think we'd be better off just assiduously hugging the query for each question we want to answer about how to get the results we want in the "moral" sphere (things that hit on your moral emotions, like empathy, indignation, etc.). Mostly I'm interested in this series of posts for the promise it presents for doing away with most of the confusion generated by wordplay such as "objective ethics," which I consider to be just an artifact of language.