In June of this year I introduced my Common Lisp library cl-cmark (GitHub mirror), which implements parsing [CommonMark] documents and manipulating the resulting document tree. I have been hammering out the last kinks over the past weeks and I am now ready to call it done. Before I officially put the 1.0 stamp on it though I would like if a few more people could take a look at the library and give it a try.
I have filed a request (#2230) for inclusion in Quicklisp. Until then you will have to check out the library from source. If you have any suggestions or issues please open an issue on GitLab or GitHub.