The Markdown export back-end,
md, converts an Org file to a Markdown
format, as defined at http://daringfireball.net/projects/markdown/.
md is built on top of the HTML back-end, any Org constructs not
supported by Markdown, such as tables, the underlying
(see HTML export) converts them.
org-md-headline-style, markdown export can generate headlines
atx limits headline
levels to two.
setext limits headline levels to six. Beyond these
limits, the export back-end converts headlines to lists. To set a limit to a
level before the absolute limit (see Export settings).