The post was just a nice thing, a complete change of pace, and an opportunity to have an interesting conversation about something we normally wouldn't. That's on topic for HN. It doesn't mean the same thing would be on topic tomorrow—in fact it wouldn't, because avoiding repetition is one of the main functions here.
It was also a garish opportunity for flamewar, which plenty of commenters unfortunately took advantage of. But that's how the internet, and human nature, work.