While in principle I agree, I think you may also want to consider the fact that most people do not have formal training in engineering (or anything technical, for that matter). Most HN readers probably do, but what if the article wasn't written specifically for HN readers? So this way of thinking systematically is new/unfamiliar for a lot of people.

I would argue that 'common sense' needs to be consciously considered and validated before it becomes common sense <em>to you</em>. So in that regard, since it's so obvious already, I doubt the author had you in mind when he wrote the article :)