I'm actually surprised that this article made the homepage and has received the upvotes it has on this (typically SEO sceptical) HN forum.

Probably less than 30% of the article would be considered "effective" (e.g. the advice is specific to, and likely to materially increase SEO performance) and the rest is either unsubstantiated (semantic tags and image compression leading to SEO ranking improvements) or unrelated to actual SEO (404 pages and other "engagement" advice).

There are much better articles that break down the basics, ignore the "SEO" parroting and that are substantiated by real data (based on test and trial).