You'd be surprised how many authors of libraries have never heard of that lesson. A lot depends on how you learned to code and whether or not you were exposed to good programming practices. Universities tend to teach you that in a rote-learning way, which is as if they didn't teach you at all. And self-directed learners tend to encounter best practices at random.

As for the scope, I think the rest of comments here show that this article is indeed in the scope of Hacker News.