Oh, I haven't seen r/rationalistdiaspora for a long time.

Looking there: The front page contains 25 posts, each of them is 2 days old, most of them don't have any upvotes, none of them has comments.

Nope. When people don't vote or comment, slow down. Only choose the best stuff, or perhaps if you believe there is so much great content, create an article containing more links.

Also, I guess you have to somehow create the initial community, to get the ball rolling. I don't know exactly how, but some startups solve this problem by having an invitation-only phase, where you can join only if an existing user invites you, which means that you have demonstrated your interest (artificial scarcity) and also that you know at least one person who is already there, thus you will keep coming to meet them, and they will keep coming to meet you.

Okay, I admit there is more than just having a good censor.