It's surprising to think that they've created all the backstory, throughout Azeroth, in just 511 characters at a time. But even Kaplan said the limit is a good thing: it means Blizzard has to show story to the player rather than tell it.
Still, doesn't seem easy to
Crap. Out of room -- that's 511 characters. Of course, they can fudge things a bit by having those "story quests" where characters can use multiple pages to build up their background, and the 511-character limit doesn't apply to all of the dialogue -- some of the later quests have pages and pages of dialogue as the quest goes on. But squeezing enough information to keep a player interested in just 511 characters is quite a feat.