Ability to use a different Markdown → HTML converter
Currently, when composing Markdown and sending as HTML, the parser used is the cmark library. However, there are many flavors and implementations of Markdown, and cmark does not fit all use cases. For example, it cannot do syntax highlighting.
To accommodate such use cases, an option could be provided in order to trade cmark for an external Markdown parser that reads Markdown on stdin and outputs HTML on stdout.
Originally discussed here.