Available to everybody by clicking on the link labeled “past” at the top. I don’t know why you chose to highlight those specific four submissions – only one of those received any comments, and that one got a total of three comments.
Not that it matters, but this was the submission that garnered, I believe, the most traction.
On topic: I was just mentioned this book to a coworker last week. I highly suggest Scott Adams' book How to Fail at Almost Anything and Still Win Big.
What's happening is it's getting a lot cheaper to buy votes on Hacker News. People have offered to do it for me to get the O(n) search papers I resubmit every quarter to the front page. Folks assure me "it's way cheaper than it used to be!"
Why would anyone do that? In particular, why would anyone pay to get an article on HN that has been there before?
Why does anyone pay money to promote anything when often you can simply deal directly with the aggregator: the illusion of authenticity and relevance.