Well lets just stick to only this form then, for lazy meta data description. I have not seen many objection to this form. Just don’t stack it. It’s in YAML.
| !CommonMark: 0.1.23-github.username.projectname
| title: Title for the top bar of any browser
| layout: report
I would probably still use the Jekyll style front matter as it does not require the writer to add | at the start of every line. It’s also consistent with how code blocks are written. No strong objection to including both though.
Actually, there is an objection. Pandoc uses a pipe at the start of a line to represent a line block. I think this is the equivalent of the <pre> tag in HTML. It looks like a useful extension to have.
Perhaps something similar to Pandoc metadata blocks could be supported instead, e.g.
% title: Title for the top bar of any browser
% layout: report