[adamzerner]

I think you get it at 500 karma.

Maybe it'd be a good idea for the site admins to check the first 5-10 downvotes of someone who just received downvoting privileges, and if they're inappropriately used, take the downvoting privileges away from that person.

[hibikir]

Some sort of double checking of downvotes is pretty common in many places that do support them. We had metamoderation even in good old slashdot.

Now, at least there are plenty of HN users that are active looking at downvoted content, and bringing it back up if they think the downvote was unfair. This behavior could be used to evaluate frequent downvoters: If someone consistently downvotes comments that end up in the positives, then maybe their downvoting privileges should be revoked.

An algorithm like that should be pretty easy to tweak too: Start with removing, say, the bottom 1% in ranked downvoting quality, and alter it as needed.

[adamzerner]

Ah, great idea!