[scythe]

It's worth remembering that a particular flaw of IRV which is not shared by all multiple selection voting systems is that it can incentivize putting a low-popularity party ahead of your more popular preference, since your vote will very likely transfer. This is called "non-monotonicity" and has been documented e.g. here:

https://www.abc.net.au/news/2011-05-04/an-example-of-non-mon...

But the Australian system is still much better than the first-choice-only method used in most electorates. You don't have the situation (discussed in the article) where an extreme faction can usurp a major party by being unified in the primaries. By shuttling "One Nation" voters to their own party, you give them a little representation, but you keep a lid on it. Meanwhile, you give a voice to new perspectives that might be ignored for a long time in a two-party system.