Oh, yes. I had also tried that, but found some convenient features missing, e.g. line breaks treated as `<br>` (not two consecutive blank lines), GitHub-flavore

Oh, yes. I had also tried that, but found some convenient features missing, e.g. line breaks treated as `<br>` (not two consecutive blank lines), GitHub-flavored tables, and the strikethrough syntax. I'll have to wait until the official CommonMark spec includes them. Also the third-party CommonMark libraries are usually easier to extend, with your own syntax addition.