A big difference between ReST and Markdown is that it's very easy to accidentally write ReST that is either invalid or doesn't mean what you think it means. The Julia manual used to be written in ReST and even people (or maybe especially people) who were pretty deep down the ReST features rabbithole, regularly committed ReST that was just wrong – quotes where code was intended; incorrect hyperlinks (why is the hyperlink format in ReST so damned complicated and non-uniform – it's basically impossible to remember); bullets or lists that aren't actually bullets or lists. This is possible in Markdown, but it's much harder: by design, things almost always mean what they look like they mean. That's a huge benefit. The Julia docs are now in Markdown and accidentally broken markup is hardly ever a problem anymore.