As someone with a degenerative eye disease (keratoconus) I almost universally hit ctrl++ about 5 times upon opening any article on hackernews. Heck, I view the HN itself at 300% size.
blog site is very readable, even without enabling reader mode. The main problem for usability are sites that mess up with the zoom, so that when you enlarge the view the formatting breaks and the text becomes unreadable.