Markdown is a faux-HTML syntax that is actually more complicated to learn than real HTML, which can be used directly and need not rely on the intermediary of a Markdown interpreter. As such, people like Kevin Lipe are quite wrong to recommend it, even to beginners.
Such recommendations stem from the myth that one must actually type out HTML elements, which is not difficult in the first place. The same text editor (e.g., BBEdit) into which you type Markdown can add valid, semantic HTML to your text automatically. I effortlessly write perfect code with such a system and it takes me no time at all. I don’t need a crutch and you don’t either. I certainly don’t need a picture of a crutch, an image to which I would compare Markdown. Indeed, Markdown is a joke that comedy nerds insist meets a legal definition of “funny” that nobody in the audience laughs at.