Gruber is famously protective of the original Markdown specification and his specific use case. He’s reacting to others’ expectations and clarifying his position that a “Markdown editor” is a bit of an oxymoron. He supports that position by reiterating his inspiration for creating the format.
I understand his point, but I disagree with it. Markdown wasn’t invented for the purposes we use it for today, true. And yet the most popular programming editor today is a website running inside a modified browser, themed with CSS and extended with JavaScript.
We have a tendency, as a group, to push things beyond their original intent.