Slashdot died from the incoming content, not the posts, as far as I recall from those days. Digg suffered the same fate. Reddit has so far been kept from it since moderators can only pin a few posts and only have "negative" control of the posts that appear at the top.

Yes, I was there. :) 23 years ago ;) I meant some sort of mechanism to improve the training/fairness/consistency of moderators rather than merely double-checking them.

Their metamoderation was innovative but ultimately pointless.

Instead of having one popularity contest, it was like a popularity contest that qualified you for another popularity contest. Theoretically the metamods were "good" posters, but being a "good" poster was ridiculously easy - you could just rack up karma by parroting the hivemind and bashing Microsoft or whatever.

That's true. If a community platform's moderation were more professional like the example I used of bar exam graders, who grade practice samples and do other calibration exercises, it would improve the signal and tend to reduce biases if the culture were one of strict professionalism.