[NathanielLovin]

Arrow's impossibility theorem only applies to ordinal voting systems. Quadratic voting is a cardinal system. Cardinal voting still isn't perfect, but it does get around some of the problems with ordinal systems.

[notahacker]

This form of cardinal voting has a particularly egregious equivalent of the "additional candidate affects preference ordering" issue in ordinal voting systems though. Unlike the weird edge cases with preference ordering in ordinal votes, the effects of adding additional votes on reducing certain voting blocs' influence on other issues where ppeoplemust divide a budget across multiple issues often lead to intuitive (trivially simple, even) strategies to manipulate a particular outcome.

If you can add a proposition to the ballot paper which sufficiently threatens a particular group, they're forced to waste votes defending themselves against it, which means they have less influence on other issues they might also care about. As far as I can see the quadratic nature makes it worse, by making it more plausible a minority could actually lose a vote that threatens them if they only spent most of their credits defending themselves against it.

That's a bigger UX issue than non-sophisticated voters not really grasping the budgeting detail.

[contravariant]

I'm not sure quadratic voting is the best cardinal voting system though. In particular it still fails to satisfy independence of irrelevant alternatives. So sure Arrow's impossibility may not apply, but the conclusion isn't actually different.