If I'm going to use something more complicated than gemtext, I'd prefer something with tables. So, not CommonMark (or MFM? Does MFM have tables?) But GFM and MultiMarkdown are fine.
@star the shitty noncompliant markdown i made aaages ago called pregdown which is secretly just a bunch of regex functions in php to convert it into html, and has support for centering text and granular font resizing among other things