I remember back in very early GitHub days we had to choose between Textile and Markdown for formatting text entry, and it was very much not a decided thing back then.
We liked Markdown better and put a lot of effort into making it work in the GitHub context (GitHub Flavored Markdown), plus adding emoji support (type colon and get auto-complete on emoji names) extremely early too.
We also made a controversial decision to add filename extension support to the Readme file (e.g.
Readme.md, Readme.txt, etc) so we could properly format your Readme file. Before that, the standard was a bare "README" file and no expectation on formatting whatsoever. Now almost every Readme has a filetype extension. In fact, of the 25 currently trending GitHub repos, 24/25 have a "
Readme.md" file (and one has no Readme at all).
Having the industry mostly standardize on Markdown has been a big productivity boost enhancer!
Markdown is the greatest advancement in tech in the past 20 years.