I am honestly not sure we can say that at all. I thoroughly enjoy both hn and reddit, for completely different reasons. Sure, from a strictly legal standpoint, it isn't censorship or a constitutional issue, but at the same time, the "anything goes" attitude in places like 4chan and reddit allow for a lot of creative gems and interesting discussion. People instinctively recognize that while you may have to schlep thought he muck to find those gems, it is still important to have an "anything goes place". People will feel betrayed when they put time and effort into making the community what it is, and suddenly the rules are changed on them -- all their effort has been co-opted or may be co-opted, for something they don't want. It feels slimy.
(yes we are all aware there is no contract or law or whatever, blah blah legalistic point missing, but the decency of it is still in question).
All that being said, I also like the curated, well organized topical community of HN, because sometimes I just don't want to wade through the crap, but that occasional preference switch doesn't diminish either form of community building.