David Rothman writes: The Thin Helvetica Syndrome arises from the latest Kindle upgrade and has made e-books less readable for some. In the past, e-book-lovers who needed more perceived-contrast between text and background could find at least partial relief in Helvetica because the font was heavy by Kindle standards. But now some users complain that the 5.7.2 upgrade actually made Helvetica thinner. Of course, the real cure would be an all-text bold option for people who need it, or even a way to adjust font weight, a feature of Kobo devices. But Amazon stubbornly keeps ignoring user pleas even though the cost of adding either feature would be minimal. Isn't this supposed to be a customer-centric company?