> Markdown’s job is... communicating to software
No, that’s a misunderstanding. Markdown is, as I said, a formalization of existing practice. Nobody’s supposed to be “writing Markdown” (except computers that generate it.) You’re supposed to be writing plaintext styled text the same way you always have been in plaintext text inputs. Markdown is supposed to come along and pick up the pieces and turn them into rich text to the best of its ability. Where it fails, it leaves behind the original styled text, which retains the same communication semantics to other humans that the post-transformation rich text would.
The ideal Markdown parser isn’t a grammar/ruleset, but an ML system that understands, learns, and evolves over time with how humans use ASCII art to style plaintext. It’s an autoencoder between streams of ASCII-art text and the production of an AST. (In training such a system, it’d probably also learn—whether you’d like it to or not—to encode ASCII-art smilies as emoji; to encode entirely-parenthetical paragraphs as floating sidebars; to generate tables of contents; etc. These are all “in scope” for the concept of Markdown.)
In short: you aren’t supposed to learn Markdown; Markdown is supposed to learn you (the general “you”, i.e. humans who write in plaintext) and your way of expressing styles.
If there’s any required syntax in Markdown that a human unversed in Markdown wouldn’t understand at first glance as part of a plaintext e-mail, then Markdown as a project has failed. (This is partly why Markdown doesn’t cover every potentially kind of formatting: some rich-text formatting tags just don’t have any ASCII-art-styled plaintext conventions that people will recognize, so Markdown cannot include them. That’s where Markdown expects you to just write HTML instead, because at that point you’ve left the domain of the “things non-computer people reading will understand”, so you may as well use a powerful explicit formal language, rather than a conventional one.)
