Yeah, I think there should be a simple explanation, maybe just in the form of what your plugin structure needs to be, without just saying it's a "visitor" and hope someone will understand what that means.
@zephraph Hey, btw, while you're here (possibly), did I tell you that started a postcss-less plugin? I got stuck when I was trying to get tests to work.
But I was successfully converting an evaluated Less tree into a PostCSS tree. You'd probably be interested in looking at that.