RE: Referenda that represent the minority
So you made me look up Prisoner's dilemma on my own.....interesting.
As I read your piece I kept thinking about the primary system in the US. This is where a committed minority becomes the filter for the candidates and policies everybody else lives by. In 2018, for example, 19.9% of the electorate participated in the primaries overall. Not only are candidates selected in the primaries, but also critical referendum are decided. In this past primary (NY) a critical green space referendum was on the ballot. Of the 19.9%, few had read about it in advance. Which meant, the people who had a vested interest in the outcome determined that outcome.
Ultimately, elections become a function of machine politics. The party with an effective, ongoing, get-out the vote system gets the candidate and policies it prefers. This is how the Democratic party got stuck with Hillary. The party machine just filtered out opposition candidates, and ideas, starting at the lowest level until she became 'inevitable.'
So, maybe not a 2.5% threshold, but 19.0 isn't representative either.
Based on the problems with these type of voting processes you would expect that the voting systems would evolve. The unfortunate circumstance seems to be that because the current systems are skewed towards the parties who are currently in power there is little room for change in political environments where only a few political parties control everything.
In a many party system I would think it logical that you can only vote in a primary if you are a member of that specific party. But in the US there is huge political spectrum within the democrats and the republicans that voters should have some influence. Breaking up parties would seems to resolve some of the problems.
The Dutch political system is actually quite good in that respect. It is a many party system. So even though occasionaly bad laws get introduced there seems to sufficient consensus to realize when a law is a bad implementation of an idea.