Everytime on groups that share a userbase with Reddit, and on YouTube, you get haters. You don't know who, you don't know why, they just downvotes and burry your comment and they're not able to comment back.
It kills online discussions, make an echo chamber for the leading opinion, and kills any content that's a bit different.
For exemple, some awesome song about Assassin's creed was featured on YouTube, a few years ago, next to related content. (Assassin des templiers)
The quality and the realisation were sublime.
But it got tons of thumbs down because it was in French, and haters only want content in English (filtering your exposition to international content was not the point of upvotes and downvotes!)
So downvotes are pointless imo. It's great they get rid of it (and HN should do the same for the quality of the discussion)