I found out that some features of MultiMarkdown are not supported in Editorial, as well as a bug:

Bug:

• Within Code delimiter (```), <> are not escaped. i.e. HTML codes within code block will still be HTML codes, not plain text.

Does not support:

• MMD metadata block (e.g. title is ignored)
• superscript & subscript (e.g. if MultiMarkdown is not selected, there's an option to select superscript. But once MMD is enabled, MMD styled superscript and subscript is not supported)
• Abbreviations
• Inline footnote
• ``this kind of smart quote'' will not resulted in “this”
• Code class (e.g. "```tex" should becomes <code class="tex">...)
• Math class (it doesn't have <span class="math">... enclosing the math)

Editorial renders footnotes incorrectly if 2 footnotes are not separated by a linebreak. MWE:

- test [^1]
- test [^2]

[^1]: ok
[^2]: should be ok but not in Editorial

In MultiMarkdown (and pandoc) however it is fine.