Isn't it a bit early to have thoughts about something we don't know the UI/UX of? Could be that "Markdown support" is just "Import/Export as Markdown", or even just export. Or it could be a fully fledged WYSIWYG editor.
The rumors seem to indicate just "Export as Markdown", which seems to be exactly what Gruber wants, according to the last 10% of the blogpost. So the rest is ranting against an implementation that doesn't seem like it'll happen?