Problem for me as a developer in reading about these things, is that I often end up in arguments with designers who have not read about these things, and they refuse to consider such input.
Thats really bad, these few little things are, if anything, an absolute foundation of Typography - a designer should get knowledgeable with this quite early in their formation.
They aren't really foundational, they're just a set of styles that tend to look nice and are therefore taught in introductory classes. There aren't any actual rules for things like style/taste/fashion.