This post documents a simple little trick I learned by accident in the iPhone's and iPod Touch's Notes application. By default Notes uses the "Marker Felt" font for its interface which lends itself well to the illusion that you're writing on a notepad rather than typing on a computer screen, but the letters are quite thick and I've found they tend to run together outdoors when the screen is bathed in sunlight.
If you've enabled an East Asian script such as Japanese Katakana or Korean Hangul on your iPhone keyboard, if you tap on the little sphere button to change to it and add one character, the text on the note you're editing transforms into regular, clear, easy to read sans-serif font, including the heading when you return to the main Notes menu. Beautiful!
I suspect it has something to do with the character set changing that triggers this. For example bloggers know Lucida Grande on Mac OS X and Lucida Sans Unicode on Windows NT-derived systems have excellent support for regular Roman letters as well as Japanese characters. It's likely Marker Felt on the iPhone does not have such character support; and for good reason! I couldn't imagine trying to read East Asian characters in such a thick, fuzzy font.