Markdown only? That's not "getting out of the way", it's limiting the ways of expression. Getting out of the way is providing simple defaults, why not depraving those who need more tools (HTML/CSS) of richer features.
I'd say you might want to spice up HTML with CSS if you want to achieve anything like font styling, positioning and so on. Spending time on content doesn't substitute spending time on presenting it the way you want. Blogger for example allows doing all that.
A very simple and practical example where Markdown offers no help: how can you change rtl and ltr directions of the text without CSS?
