Regarding completeness, it is not great. It was implement with an emphasiz on the indentation/prefix-related part (the hard one, I hope) so quoted blocks and and lists are almost complete (with arbitrary nesting). I did not need the other
stuff, so there is a basic support for headers, paragraphs and code
blocks. I followed the commonmark spec (
http://spec.commonmark.org/0.17/).
If there is an interest to use PetitParser/CommonMark in Pharo, I can spend some time on it. I guess, I would be able to parse majority of the examples (I am not sure about all the corner cases).
Cheers,
Jan