I don’t know if ranked choice voting really works with “tactical voting”.

So, completely ignoring the reality on the ground and just talking about it hypothetically, yes, it is possible for tactical voting to play a part.

If we imagine Greens and Labor voters would (in an honest vote) preference each other, followed by Teal, followed by the LNP (and we'll ignore any 5th parties as irrelevant), and that many of the Teal voters you describe would have begrudgingly voted LNP 2nd rather than jump ship all the way to Labor or the Greens, then supposing native Teal votes are low enough, it is sensible for Labor and Greens voters to vote tactically.

If we imagine the first round of voting comes out as:

• Greens 10% (a bit less than their national average)
• Teals 20% (an easier round number, close to that 18% figure quoted below)
• Labor 30%
• LNP 40%

With honest voting distributed as described above, the Greens are eliminated first, taking Labor to 40%, and then the Teals are eliminated, giving the LNP a win with 60%.

If instead some portion of Greens and Labor vote tactically, the first round might end up as

• Greens 5%
• Labor 20%
• Teals 35%
• LNP 40%

Which sees first Greens, then Labor, eliminated, resulting in 60–40 Teal win.

It's an edge case and may or may not reflect the reality of how voters felt at the election. And tactical voting in IRV is very unreliable and requires much more specific knowledge of how other voters are going to vote in order for it to pay off than in FPTP. That same tactical voting could have hurt their more-preferred option if, say, the actual honest percentages had been

• Greens 12%
• Teals 15%
• Labor 33%
• LNP 40%

And 6% points of those Teals chose Labor, resulting in Labor getting 45% after Greens are eliminated, and then 51% after the Teals are. The strategic voting of Labor and Greens if this were the true preferences would have given it to the Teals despite Labor being the winner in an honest vote. Despite only a fairly small and difficult-to-predict change in the honest intentions.

Tagging @Ilandar@aussie.zone for interest's sake, as well as @hanrahan@slrpnk.net.

Sure, what I have is anecdata, but I will say the study is focused on the teal voters, whereas the people I’m talking about were members or organisers.

Fair enough. You did specifically talk about voters in that previous comment, though, not members or organisers.

I don’t think that’s a good read of what’s happened given the “teal” voters I know about. Almost to a person, Teal voters are ex-Liberal voters.

overall the way most people vote is to put the candidate they like the most at the top, and the candidates they like the least at the bottom. If they distrust the majors, they put the majors “later”. Basically, if you think the Teals are going to get up, but you want the Greens, you’re still better off putting the Greens on top.

I agree with this under normal circumstances, but keep in mind that the Teal candidates were not established independents, nor was the movement itself. In that sense I don't think they can really be considered as "majors" - they were potentially still outsiders. I think an example of what the study is suggesting could be that both Labor and Greens voters believed the Teals had a better chance of beating the Liberal incumbent but only if the Teal candidate survived until later rounds. For that to happen, they needed first preference votes so these voters were "tactical" in the sense that they voted to give the Teal candidate the best shot at defeating the Liberal incumbent - even at the expense of their preferred candidate.

A similar, but slightly different, method of "tactical" voting in this scenario would be to give the Teal candidate your first preference in the hope that they received a majority. I also witnessed members of my family who are consistent Greens voters employing this thought process at the previous election due to their desperation to see the Liberal incumbent removed from office. They gave the Labor candidate their first preference, hoping others would do the same and that he would win on a majority. It made less sense in our electorate, since the Labor candidate was also going to be competing against the Liberal candidate in the final round of counting. As the study noted, the voting strategies in these Teal electorates were highly unusual so I'm not sure you can use normal Australian voting habits to dismiss the findings of the researchers.

I think what’s happened is that they’re looking at 2019, the Scomo era. By that era, the voters I’ve been talking about would already have shifted to Labor or the Greens as Option 1, something they would not actually want, they just wanted a Scomo Coalition even less. I think the Teals actually are the first preference here, and a lot of these guys used to vote LNP in maybe 2015.

This seems like it could be a contributing factor, for sure. The criteria for "X voter" here is only based on how the person voted at the 2019 election - people definitely can change the way they vote from one election to another. Particularly if they have strong feelings about a particular issue (in this case it was likely climate change and gender equality).