Excuse my ignorance but why can’t an editor be implemented that uses markdown behind the scenes but is WYSIWYG? There was a similar thread over on StackOverflow:
It was mentioned that the CKeditor now can work in markdown. Even if CKeditor isn’t fit for purpose, surely the team behind Discourse could considering writing their own? How hard can it be 
I accept (even if I don’t understand the technicalities) that switching between HTML and Markdown is problematic but if Markdown has a future, then a good WYSIWYG editor would be an ideal companion?