I wrote my MA thesis in Markdown. The good thing about Markdown is that it forced you to just write and it had enough markup to be useful, but not so much thst you depend time procrastinating getting the output perfect (like LaTeX).

Pandoc can convert Markdown to .icml this is an Adobe InDesign format which allows you to go from markdown to a professional typesetting solution including figures, footnotes etc.

Of course if you write a physics or math paper there are better solutions, but for the majority of things you could write markdown is good enough and that is the reason so much of the content you encounter is in markdown.