Because the number of quotes already used is increasing, and the number of LW users is increasing, I propose that the next quotes thread should include a new rule: use the search feature to make sure your quote has not already been posted.
For a balance, once every two years there could be a thread for already posted quotes. Like "choose the best quote ever", to filter the best from the best.
Then the winning quotes could randomly appear on the LW homepage.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.