I have downvote powers and used them *extensively*. This is me on this kind of HN thread:pic.twitter.com/WdH1inmNiJ
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That's a teeny bit like how stackexchange works, although the connection is fairly weak: "experts" are identified by enough points in the relevant categories, and the abilities conferred by more points don't directly include deleting answers, but do include locking questions.
I find it surprising how good "technical" Twitter is for this. I think the SNR is maybe 1:2 to 1:10 for questions I ask here. Terrible in an absolute sense, but extraordinarily good relative to other forums I know of (including mid-sized private forums).
I expect that r/askhistorians has a higher SNR than HN due to its moderation policy. And I think HN is actually way better than the popular alternatives -- I think you'd see 2 9s deletion on HN, 3 9s or more on r/programming and slashdot.
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