HN has a downvote system as well. What you describe happens when a comment gets downvoted enough times, which makes it another good example of downvotes amplifying groupthink.
I kinda like that I only have upvote button currently here since I haven't hit the karma threshold. I do feel like the HN crowed doesn't downvote comments unless its spam or way out of the current topic. It happens but not like reddit where it acts like a disagree button.