I think our best option is to extend our RST parser (which is homegrown and already diverges from RST) to also support more markdown elements. I don't mind markdown except for its signification trailing whitespace feature (or was that removed now?) but RST is not so bad either and **all of the existing** documentation uses it...
Finally, "look at the graphs, Markdown won over RST" is a valid but terrible argument -- what's next then? Should we use braces instead of whitespace? Or direcly use Rust instead of Nim?