I've been wondering the same thing. My assumption was that it was for new links so HN doesn't get spammed to death by offering do-follow links to new stories. O

I've been wondering the same thing. My assumption was that it was for new links so HN doesn't get spammed to death by offering do-follow links to new stories. Once the link has been vetted by the community only then does it go do-follow. But thats just my $0.02.