The "HN Users, please upvote this" banner at the bottom is disconcerting. If HN is becoming a place people are desperate to get their stories voted up on, I fear the quality is going to start decreasing dramatically in the coming months.
That's a Wordpress plugin called "WP Greet Box" [1] and this message is only shown to users coming from HN, not everyone. Also, you'll be happy to know that I get grief for it every time one of my posts lands on the homepage :) I understand your concern, but it's really just a reminder to vote the article up if you enjoyed it. I frequently read good articles and then forget to vote them up because something else catc…
That way after I read the story, even if I go away, the comment page is still open so I can upvote it when I am clearing up later. In that way I rarely if ever forget to upvote a story I liked.
I don't particularly like having my upvote solicited because it makes the thing seem too much like a popularity contest - the people who lobby end up getting more than the equally worthy ones that don't.