Just from reading the web-site and looking at the images, I don't think it's clear enough as to what the editor does.

I presume you edit the document in the 'rendered' view (as opposed to the plain text), probably like in a word processor where apply formatting by selecting text and clicking buttons or pressing key-combos -- but I don't think there's anything there that clearly indicates that.

There's some degree of mixed-messages with the way in which it mentions/shows plain-text and markdown.