To use a person anecdote, when I come to HN I immediately look to the top. I have come to expect good stories up on top, and I'm sure I'm not alone in that sentiment.
This being a likely user behavior, you could game that behavior by putting 5 or so of the newest stories in a thinly bordered box, above the normal top stories. That way when people go looking for the top stories, they see the new stories, and are more likely to read and comment on the interesting ones.
This will preserve the normal UI of the site, with minor UX changes, while giving exposure to each story as it comes in. If I were to guess, most of the good stories that come in and languish do so because of a lack of exposure. I'm willing to bet that most people don't look at the newest page very often, expecting others to upvote the good stories onto the frontpage for them.