Just came back to mention that two of the most well-known Mithril-based projects, Flarum.org[1] and Lichess.org[2] are open source and have mobile UIs that you can try out, so if anyone's interested in seeing non-trivial codebases that use a "lighter approach" alluded to in this article, there you go.
Mithril is amazing. I've been using it for over a year and only like it more and more. Its fast initial load time is very relevant in today's world of mobile web apps.
I don't say Mithril is bad but code size is no indicator for performance. Counterexample: The minified Box2D code is ~760kB large and impressively performant.
The site says 12KB, for some reason, but minimized and gizipped, the latest version is closer to 7 or 8 KB IIRC.
http://mithril.js.org/