One important difference is that you need 100 karma to start downvoting people. It makes HN more resistant to invasion, though not entirely so. Perhaps people

One important difference is that you need 100 karma to start downvoting people. It makes HN more resistant to invasion, though not entirely so. Perhaps people could be required to have been members for a month before upvoting stories or something as well. Unfortunately, this requirement is less effective if people cheapen karma by not being judicious with their upvotes, as I try to be here much more so than on reddit. Upvotes effectively shape HN; upvoting witty one liners and puns, etc, is the path to becoming reddit.