Well, he is widely regarded as one of the best writers of all time and among other things won the Nobel prize in literature http://www.nobelprize.org/nobel_prizes/literature/laureates/.... Don't mistake brevity for simplicity. Btw, If you are just starting out I highly recommend The Sun Also Rises.
Have you ever thought about the possibility that the Nobel prizes aren't always fully rational or narrowly focused and that there are different motives involved? Hemingway had the novels that widely resonated. Sometimes the writing style or technical details aren't too important when you consider the work as the whole.
Basically by disallowing read access to /users in the Firebase security rules (which you should do), the latter 50% of the article would be moot. However the html injection is interesting, be extra careful to validate data when using dynamic jquery-selectors?
If you are new to Javascript you should note that this tutorial makes heavy use of Promises which is one way to handle callbacks piling up, but it's not the only way, or even the most common.
