I think there are a few things going on here that differentiate it from Digg/Reddit (I'll leave out Slashdot for the moment, because I think they have different concerns).
On Digg and Reddit, there is no "focus". Digg started out as a tech news site and degraded slowly until they opened up the doors to include all news, which brought what you have refered to as posts on Obama's latest news and pictures of their cats.
On reddit, the day I stopped reading was the day I saw a post on the front page encouraging folks to not post political stories on the politics sub-site because they don't get enough attention that way. That would imply that both sites have a problem with "activists".
To me, that sufficiently explains why the front page of HN "works". What I can't figure out is why the comments on this site tend to be so civil. The HN community seems to lack the hostility that plagues virtually every other site of its kind. Is it fewer angry people? Older, or more mature audience? Maybe it's migrants from the three sites you mention who were fed up with the poor behavior exhibited there?
On Digg and Reddit, there is no "focus". Digg started out as a tech news site and degraded slowly until they opened up the doors to include all news, which brought what you have refered to as posts on Obama's latest news and pictures of their cats.
On reddit, the day I stopped reading was the day I saw a post on the front page encouraging folks to not post political stories on the politics sub-site because they don't get enough attention that way. That would imply that both sites have a problem with "activists".
To me, that sufficiently explains why the front page of HN "works". What I can't figure out is why the comments on this site tend to be so civil. The HN community seems to lack the hostility that plagues virtually every other site of its kind. Is it fewer angry people? Older, or more mature audience? Maybe it's migrants from the three sites you mention who were fed up with the poor behavior exhibited there?