@manton I would want to separate style from semantics and perhaps have both #markdown and facets.
There's a difference between "I want this to be bold" vs "This is a hyperlink." One expresses an author's intended or requested presentation while the other codifies meaning, leaving the reader's client to Do The Right Thing for the client's situation.
In a way it's what the author wants vs what the user needs.
And a natural benefit of this is not having to worry about straining markdown with new, semantic stuff like spoiler alerts.