> it is a stepping stone to proportional representation (achieved by adopting both RCV and multi-member districts), which is much more important than which single-winner voting system is chosen
There are proportional methods for STAR and approval as well, there's no reason they couldn't be the stepping stones from this perspective
> you need to be a fellow voting systems nerd to understand when you may want to vote tactically in RCV, so approximately zero people will vote insincerely
Yet that doesn't try and stop people from duping voters into eg only ranking Palin, even though RCV is basically the only system where there is practically 0 reason to not rank additional candidates. Your point mostly makes sense but in practice I wouldn't expect high amounts of tactical voting in STAR either for similar reasons. And from another perspective - if someone were to eg bullet vote in STAR to help their first choice win, is that really tactical voting, or just an honest vote/admission that they care so much about their first choice that all other opponents are equally bad? In my opinion, being forced to grapple with compromise would be good for society.
> it is really obvious that voting tactically is an option in approval voting, and so lots of people will vote insincerely and this will undermine the confidence in the voting system
Possibly, although I think bullet voting is much less common than people think it would be. That said, people want to be able to express preferences so I think the best use of approval is in primaries where the top two candidates proceed to the general. Outside of that I'm kind of meh on approval, and if people have to choose between approval vs RCV or approval vs STAR, I expect RCV/STAR to win almost every time.
> while single-winner RCV may not result in many more third-party winners (we need multi-winner RCV, i.e. proportional representation for that), it will change the kinds of winners for the two dominant parties, which is just as important. This point is always under appreciated.
Will it? With RCV the two dominant parties no longer have to worry about the spoiler effect, so there is even less incentive to reach across the aisle and receive influence from a third party than before. Whereas before you might want to take some token talking points from a third party and siphon some votes from them, with RCV you might be able to assume you'll get those voter's 2nd choices for free.