I think it's not about readability but rather about context and the audience. On HN all caps is uncommon and, I would venture, considered somewhat aggressive/r

I think it's not about readability but rather about context and the audience. On HN all caps is uncommon and, I would venture, considered somewhat aggressive/rude. IMO HN is somewhat of a bastion of courtesy and reasoned debate, a rarity on the internet today. Long may it remain so.