Focus and good moderation. It's better to think of HN as a mid-sized, well moderated subreddit, than a comparison to Reddit as a website. You'll see that as sub

Focus and good moderation. It's better to think of HN as a mid-sized, well moderated subreddit, than a comparison to Reddit as a website. You'll see that as subreddit grow bigger and become "default", content quality often slides. This can often be stemmed by good moderation, but they only have so much power with the limited tools Reddit gives them. HN's moderators are also the programmers of this website, so if they need a new tool? Bam, new tool.