> But if you say your system uses "Markdown" then that's zero help for someone who wants to submit to you a complicated Markdown document for processing.
This "Standard" makes things even worse. There are plenty of sites already on the internet that say they accept "Markdown", and that meant something: that it implements Gruber's formatting, and perhaps some extensions (and sites with extensions are normally clear about the fact that they're extensions, e.g. "Github-flavoured Markdown"). Now people will see a site that accepts "Markdown", expect it to support a feature from "Standard Markdown", and get angry when it doesn't.
This "Standard" makes things even worse. There are plenty of sites already on the internet that say they accept "Markdown", and that meant something: that it implements Gruber's formatting, and perhaps some extensions (and sites with extensions are normally clear about the fact that they're extensions, e.g. "Github-flavoured Markdown"). Now people will see a site that accepts "Markdown", expect it to support a feature from "Standard Markdown", and get angry when it doesn't.