+++ Chris Alley [Nov 12 14 07:58 ]:
If metadata blocks (beyond the document header) are going to become a CommonMark extension, using these blocks for comments is sensible, especially as it eliminates the need for a specific Markdown comment syntax.
The Pandoc README states that a YAML metadata block can be terminated with either three hyphens or three dots. What was the reasoning behind this? I personally like the use of hyphens as a delimiter for both the start and end of the block (consistent with other parts of Markdown that use matching delimiter pairs). I see a potential clash with the horizontal rule syntax though.
The three dots YAML’s standard way of signalling the end of a YAML document within a larger file, so that’s why I used it originally. But by then the use of three hyphens for enders had caught on in Jekyll, Hackyll, etc., so I supported both.
I wasn’t actually making any concrete proposals about CommonMark here (either metadata or comments), just an observation about pandoc.