TOAST UI Editor – Markdown WYSIWYG Editor

Why do this with markdown? Github supports other [1] markup languages, many of which were designed to be edited programmatically. The format produced by such tools are not designed to be read by humans [2]. Perhaps other tools support commonmark/GFM, but not the computer editable variants listed [here][1]? But that leads to the second question: why have such tools converged so heavily on markdown?

Don't get me wrong, I love markdown, but only because it allows the author to define the formatting of their source in the way they want. Standardizing markdown is completely against to the point. If you want a standardized markup language, why not start from something well defined, that is designed to allow extension, and in fact already includes more features than markdown?

[1]: https://github.com/github/markup#markups

[2]: Markdown is harder to make ugly than html, but the OP doesn't wrap long lines, and doesn't format tables properly. They also do inline links. I've seen readme.mds in the past that numbered every entry in a list with a 1., because they know that markdown treats it all the same when rendered.