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I don't know if anybody here reads the Blog "Pharyngula" by Prof. PZ Myers. (http://scienceblogs.com/pharyngula/)
"Evolution, development, and random biological ejaculations from a godless liberal"
Anyway, when PZ has a commenter that gets on his nerve, he "disemvowels" them. Deletes all the vowels from their post.
It's more effective than banning or deleting, but it does waste space. But it drives the trolls nuts!