I've been using the distill package for writing scientific papers recently and I need to be able to have components of a yaml title that include components that are italicized, sub/super scripts, etc. For example, if the title to an article is:
title: "This <i>is</i> a *long* marked & component with $x^2$ elements but no<sub>stuff</sub> or other Action~not~ is allowed."
The only thing that renders as the title element correctly is the ampersand whereas if it is in the body of the document, all of it renders properly.
I believe this is because the title is not processed as markdown text within distill. distill make the assumption currently in several places that the title is plain text, and retrieve this information from the Rmd header to use it in HTML tags directly.
You can open an issue to ask for support of this - Not sure how simple it would be.