alt Hacker NewsI've heard the arguments for approval voting, and I'm sure it's all the things you mention and more, but people don't get it. I don't get it. I don't want to vote for both Hillary and Bernie. I want to vote for Bernie, and then only if Bernie can't win, would I let my vote go to Hillary. You can explain to me until you're blue in the face why approval is strictly better even in this situation, but I am emotionally attached to my vote counting for Bernie more than any other candidate, so reason isn't going to work on my lizard brain.
I know, it sucks. Politics is terrible. But we have some momentum behind RC/IRV so we should use it and stop the single-vote FPTP system that's plagued us for centuries. Anything is better than that. So let's join forces and get behind whatever has momentum even if it's not technically the best.
Approval voting seems to me to be worse on all counts that the previous commenter was levying against ranked-choice. To your point, the spoiler effect seems like it would be much worse with approval than with a ranked ballot, since highly partisan voters would have little reason to approve of any candidate other than the single candidate they want in office. Approving of anyone else lessens their candidate's chance of winning.
A ranked choice ballot at least requires you to assign a unique value to every candidate on the ballot: you can honestly rank your second choice without being concerned that doing so undermines your first.