That seems to be distinguishing, as the name suggests, between 'is' and 'ought', not between 'should' and 'ought'. Indeed, both the article itself, and its quotes from Hume, seem to use 'should' as nearly synonymous with 'ought'.

(Even if I've got it wrong, ryanklee claimed that "[i]t's not common" to make that distinction, and pointing to the technical work of philosophers doesn't undermine the claim about common useage.)

Back in high school, Lincoln-Douglas competitive debate taught that "should" was for practical justifications and "ought" was for ethical justifications. Again, to your point, most people don't bother to be so careful with their choices of words.

I ought to think twice before starting a comment thread on HN now