HN does have some policy around downvoting - you have to have ~600 "karma" before you can do it. Reddit doesn't any restrictions at all, and of course that's a

HN does have some policy around downvoting - you have to have ~600 "karma" before you can do it. Reddit doesn't any restrictions at all, and of course that's a massive echo-chamber. But Facebook and Instagram only have upvotes (likes) and the communities are either massive hugboxes or ghettoes.