Markdown is widely used but I agree that it's a mess, there are so many dialects.. A similar but better markup is ASCIIDOC; it's formally defined and comes wit

Markdown is widely used but I agree that it's a mess, there are so many dialects.. A similar but better markup is ASCIIDOC; it's formally defined and comes with a Technology Compatiblity Kit (TCK) that can be used to certify the compliance of an implementation with the spec.