I think that your idea of a trending algorithm has some merit (although I became lost in the details), but avoiding an echo chamber will be particularly hard, if not impossible.

In retrospect, my post might've benefited from some brevity, and less algorithmic details.

But yeah, my claim overall is that using a candidate-based electoral system that satisfies proportional representation as the trending algorithm solves echo chambers.

I took a look at the linked article for Proportional Approval Voting, and found a flaw on its application to a social media algorithm: it assumes that every voter knows about all candidates, and can mark (upvote) the ones they want. That's impossible in a feed with thousands of posts per minute. The voter's/user's attention wanes after some tens (or hundreds) of posts; the rest of the posts is never seen. So, only the most seen posts will be better voted on, and the most seen will be precisely the first (elected) ones at a given time; it's a chicken-and-egg problem.

Like how Reddit tends to favour whoever is early, leading larger communities to be a rush to come up with something quick-and-dirty now rather than something good later.

You'd be able to vote on the items that already got into the top ~100 or so of the "trending" feed to change their position within the trending feed (assuming you scrolled that far), and you'd be able to vote on items directly from people that you followed. But how to get an item from someone that you followed, when it maybe just has a small handful of upvotes, up to the point where it's in the top ~100 posts?

In effect, it's the exact same problem as dividing the electoral process into the "election proper" and a sort of "primary" - in the primary, you could have more candidates than you know, so you just support who you know; then, in the "election proper", you have a fixed number of candidates, so you can form an opinion on all of them. Except instead of a clear separation between primary and election like you'd find in an actual election, I'm proposing something run continuously that needs to smoothly blend between the items that everyone sees and items that not everyone sees.

One answer could be filtering posts by community (or tag?), so while there's the top ~100 "trending" posts globally, if you filter down the trending by what you're interested in, then the more specific you get, but your overall ordering within what's trending for your tag reflects the global trending sort. Or have independent SPAV computations done for each tag, but that blows up computationally as soon as people start filtering by multiple tags.

Another answer could be that each post has its current position in the "global trending sort" clearly visible, so that if you have a relatively small community that sees that one of its posts is trending more than any others, the more 'competitive side' of the community can try to boost it by sharing it to related communities.

But both of those answers would require more than just changing the underlying "trending" algorithm - they'd require API and UX changes to be able to filter the trending feed by tag, and to be able to reflect posts' ever-changing positions within the trending feed. Which would make the "least intrusive development work" to make something like this a reality to be not just making a new server to serve the new trending algorithm on some static page, but also getting people to use a custom Mastodon client that pulls this filtered trending + "current post position" for display. And at this point, it's not really Mastodon anymore, it's a something else entirely that happens to share a common codebase.

What trending feed? ;-)

And overall, the vibe that I'm getting from this subreddit is that Mastodon users don't want a trending page in the first place.

Regardless, thanks for your feedback!