If you look at the sidebar and the URL, you'll see this is one page out of a set of notes on ZDDs. That is why BDD's are just touched upon. The real question

If you look at the sidebar and the URL, you'll see this is one page out of a set of notes on ZDDs. That is why BDD's are just touched upon. The real question is why was this particular link submitted as newsworthy and why did it get to the front page of HN? It is just a sidebar on the thing the author was actually writing about.