I was a bit disappointed in this article for the same reason: this is a great primer for people new to MPEG video compression, but it doesn't have anything to do with H.264.

I was hoping the author would write about H.264 specifically, for instance, how it was basically the "dumping ground" of all the little tweaks and improvements that were pulled out of MPEG-4 for one reason or another (usually because they were too computationally expensive), and why, as a result, it has thousands of different combinations of features that are extremely complicated to support, which is why it had to be grouped into "profiles" (e.g., Baseline, Main, High): http://blog.mediacoderhq.com/h264-profiles-and-levels/

I was also hoping that he would at least touch on the features that make H.264 unique from previous MPEG standards, like in-loop deblocking, CABAC Entropy Coding, etc..

Again, it's fine as an introduction to video encoding, but there's nothing in here specific to H.264.

... but Diet Coke doesn't have sugar in it, so it shouldn't cause cavities, right? Did a joke just go over my head or am I missing something?

Diet coke has phosphoric acid which causes erosion of the enamel.

It's not the phosphoric acid, its the carbonation. Plain old carbonated water is acidic as well which can erode the teeth. That being said your saliva can repair the teeth. The current wisdom is don't drink solely acidic drinks and wait between acidic food/drink and teeth brushing.

Or chew gum with xylitol (It's actually natural birch sugar) that will heighten the PH level and kill germs.