I'll give you one example that I saw just now of someone else's comment that was downvoted.

https://news.ycombinator.com/item?id=43710265

It happens all the time.

Here's an example of my comment on the same topic.

https://news.ycombinator.com/item?id=43256114

The tone policing one has to do has to be done only by one side, the other "side" can write very low quality comments with personal attacks and not get downvoted or flagged as frequently. It's same on Reddit too. Absolute misinformation and FUD gets voted up if they favor the prevalent side and countering comments are downvoted creating a chilling effect to reduce visibility and discourage participation of folks that don't agree 100% with the political narrative.

That is exactly how Reddit became more and more extreme leading to popular subs becoming full of death threats at one point. And HN is on it's way there.