I am sincere. You've picked some pretty obvious differences. I'm talking about the vast majority of fonts which are to all intents and purposes identical. I don't know if you have a kindle but to restate my original question - if you read the same book using each of the 8 or so built-in fonts, do you seriously believe you are reading 8 different books? I'm sorry, it's just a nonsense. Sure, you can have a favourite font or dislike how..i dunno..descending letters look, but I simply don't believe normal human beings look at a (normal, not comic-sans etc) font and a) give a shit about it, and 2) feel that one is more "professional" or "zippy" or some other adjective, like a designer has reached into their soul.