[godelski]

I'm glad you brought this up, because ~RCV~IRV does not actually satisfy these conditions (it is a personal point of frustration how Fair Vote is misleading, even by using the term RCV). IRV doesn't pass the favorite betrayal criteria. IRV also causes a weaker definition of what it means to be a spoiler[1]. Specifically you should look at monotonicity[2].

I'd encourage you to dig a bit into electionscience.org (they have some good YouTube videos as well) as they do a deeper dive on some of these topics. There's a reason Arrow himself was a fan or cardinal systems. The other part is that we need to consider factors other than VSE and spoilers. A lot of people get hyper focused on VSE (typically Condorcet supporters) and while it is an important factor 0.5% isn't a big deal (really a few percent isn't). Also you might want to check out our (HN) resident voting expert's[3] comments, because he links to a lot more information. I'd call myself a hobbyist where Clay is an expert.

[0] https://electowiki.org/wiki/Favorite_betrayal_criterion

[1] https://electionscience.org/library/the-spoiler-effect/

[2] https://electionscience.org/library/monotonicity/

[3] https://news.ycombinator.com/user?id=ClayShentrup