I'd suggest deletion removes the account entirely, and has an option for deleting all posts that is of by default. Posts from deleted accounts should simply say "deleted account" as the poster. There should be an extra, trivial inconvenience added for deleting all the posts to discourage people from doing it.
At 2011-04-08 LW user account deletion is broken. We (Trike) will fix it… but how should it work?
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