All right, let me offer a different phrasing: Aaron Swartz created atx, and John Gruber created Markdown. The syntax between the two is similar, but not identic

All right, let me offer a different phrasing: Aaron Swartz created atx, and John Gruber created Markdown. The syntax between the two is similar, but not identical, as can be said for several other "plain text markup" formats that are, you know, not Markdown. (Like Textile, which was also not created by Aaron Swartz.) Not insignificantly, the original Perl script that implements Markdown was John Gruber's. It functions as a plugin for the Perl-based Movable Type blog engine because that's what Daring Fireball uses. Swartz wrote atx, by contrast, in his preferred programming language of Python. So, to be factual: John Gruber created Markdown.