(I've mostly only skimmed.)

It can be hard to find good content in the diaspora. Possible solution: Weekly "diaspora roundup" posts to Less Wrong. I'm too busy to do this, but anyone else is more than welcome to (assuming both people reading LW and people in the diaspora want it).

This is what /r/RationalistDiaspora was intended to do. It never really got traction, and is basically dead now, but it still strikes me as a good solution. If that's not going to revive though, I agree that a weekly thread on LW is worth trying. By default, I'll make one later this week. (I'm not currently sure I'll have anything to post in it myself, I'll be asking people to post links in the comments.)

Go tell Scott Alexander you'll build an online forum to his specification, with SSC community feedback, to provide a better solution for his overflowing open threads.

He tried to move people to /r/SlateStarCodex, but that didn't work. We'd want to understand why. (Some hypotheses: it wasn't actually on SSC, where people go directly; posts there don't pop up in their RSS readers; people have an aversion to comment systems with voting; people have an aversion to reddit specifically.)

As Scott features more and more posts, he gains a moderation team full of people who wrote posts that were good enough to feature.

I'm not sure that "writes good posts" and "would make a good moderator" are sufficiently correlated for this to work. A lot of people like Eliezer's writing but dislike his approach to moderation.

(On the other hand: maybe, if we want Eliezers to stick around, we need them to be able to shape the community? Even if that means upsetting people who don't write much.)

It also creates weird incentives, like: "I liked this post that was highly critical of our community, but I don't want the author to be a mod". (This is the problem that Scott Aa points to of "this system can only improve on ordinary democracy if the trust network has some other purpose" - I worry that voting-for-comment-scores isn't a sufficiently strong purpose to outweigh voting-for-moderators.)

Another system to consider would be to do it based on the way people administer votes, not the way they remove them. If your votes tend to correlate with others', they have more weight in future. If posts you flag tend to get removed, your flags count for more. (I'm not convinced that this works either.)