I was perusing some old blog posts and stumbled across this old RSA about the Read Languages spell. It got me thinking about the "Common Tongue" conceit in D&D. Other games have their versions as well; Runequest's "Tradetalk" springs to mind. In the post I mention that the spell doesn't seem to see a lot of use in-game and being a stickler GM about languages can be potentially annoying/un-fun for the players.
So here's an idea: the Common Tongue is just that; a tongue. i.e. a spoken language. That means there IS no written form. It's a pidgin of various words and grammars into an almost slang. Sure you can chat up the shopkeeper in Common, but odds are the sign on his door is in his native language.
This can open up more reasons that learning a language can matter as well as knowing the Read Languages spell. It's not TOO punitive, because it doesn't preclude all communication. It just makes knowledge a tad more useful. Which can be really handy in old-school games where that 16 INT magic-user knows five languages, but is tapped out on spells for the day.