If it were a WYSIWYG editor, there'd be previews for images. But it seems like it's just syntax highlighting for textareas. Nice project either way, but false advertising.
WYSIWYG does not refer to the icons in the toolbar, but rather the text itself. This is not WYSIWYG because when I make something bold, I see a bunch of asterisks around it.
Still a cool project, but someone who does not understand markdown would wonder why pressing the heading button makes my text into a hashtag instead of making it bigger.