[duskwuff]

Would also punish users for posting rebuttals to controversial or factually incorrect posts. I feel like that's a net negative.

[brokenmachine]

That's sort of what happens on reddit.

Often I feel it's not worth replying to obviously wrong stuff because it'll just get downvoted so low that nobody's likely to see my eloquent and carefully-worded rebuttal anyway.

[beachy]

Perhaps an additional feature to explicitly mark your post as "rebuttal"? Then only the non-rebuttals would inherit the downvote?

[duskwuff]

And why would users not simply mark all of their posts as rebuttals? There'd be no downside.

[beachy]

Because rebutting something that was subsequently upvoted would incur a downvote!