MultiMarkdown is Markdown dialect.
It is used in Scrivener (which also allow pandoc-Markdown export), and iWriter Pro.
It has its own style of frontmatter, e.g.
Title: A Sample MultiMarkdown Document
Author: Fletcher T. Penney
Date: February 9, 2011
Comment: This is a comment intended to demonstrate
metadata that spans multiple lines, yet
is treated as a single value.
CSS: http://example.com/standard.css
… body of the document here …