Meta comment, but I would love for there to be more insight into the sociology of Hacker News. I feel like in the last couple of years we've seen a stark decrease in the frequency of "What to expect when you're expecting (to be a millionaire founder)" articles and a stark increase in "Enterprise Patterns" discourse. The latter is oddly at pretty serious tension with PG's ideas about development and Scheme.
I find the "Liskov Substitution Principle" is an awkward way of pointing at the idea that your usage of subtyping should not render the type variance in your system nonsensical.
It's cyclic. When I first joined over a decade ago there seemed to be a lot of technical posts and discussion at the time, which gave way to a lot of SEO discussions, which gave way to technical discussions, then shit tons of Erlang (not that I minded), then other stuff for founders, etc. People tend to post interesting things which leads to other interesting and related things. So you'll see a lot of a certain topic or field, maybe a surge in new users or user activity because it interests them, and then some new topic or field becomes dominant for a while and appeals to a different subset of users who become a bit more active with submitting, posting, and voting.
I find the "Liskov Substitution Principle" is an awkward way of pointing at the idea that your usage of subtyping should not render the type variance in your system nonsensical.