It’s meant as an interesting CSS hack to make markup look like markdown, but still function as regular HTML (including having things like links still work). There are thousands of things that compile markdown to HTML, that's not at all what this does. Try clicking on the different tabs to show the different states or the demo link to the left of them—maybe that'll make more sense?
I still don't get it, why should I make something look like markdown when it can be actual markdown. Links work in markdown, you can eve use something like maruku to have html elements (divs, id's etc) in actual markdown.