Using a serif font would allow easier distinguishing letters such as "I" and "l"
We're working on making it easier to distinguish between those two letters.
I agree. I recently had trouble telling apart "lo" (the) from "Io" (I) in the Italian lessons because of this, so I had to guess which one was which. This is how it went: http://s15.postimage.org/lsg7w988b/image.jpg
Curse you Helvetica.
I vote for another font too. This is very annoying.