Bit confused by this comment. I don't think anybody suggested you're going to find these things solely by interacting with the terminal - but rather through "out of band information" as you put it, which in GP's case, as he said, was a book. The surprising part of TFA, and replies to my comment - to me anyway - is how one can go so many years without picking up that information.
I have never read a book about improving my terminal knowledge. I have a few tricks I have picked up over time (probably through posts like this!), but never done holistic research on the subject. Therefore, despite having used the terminal for decades, I likely have a similarly long list of basic terminal knowledge gaps. I do not know what I do not know.
