First, kudos to the author for this approach. I avoided the hell out of react for the longest time because of the JavaScript build soup you seemingly needed to get anything to run. I would've loved a tut like this a year ago.

> At it’s most basic, React is a tool for rendering HTML with JavaScript.

Not really; at its most basic, it's a tool that inextricably ties DOM state with JavaScript (a conceptual implementation of WebComponents). That's the power of React. Yes, a byproduct of that is that it renders HTML, but you use it so you don't have to use things like Sizzle to get into and manage the state of the DOM. Its a small difference but meaningful in that you wouldn't want to confuse its purpose with something like document.createElement().