It'd be interesting to see Twitter adopt the old "Robot 9000" automod rules, where every tweet would have to be unique from all previous tweets system-wide or else you get a temporary ban that exponentially grows in length after every infraction.
/r9k/ was actually modeled after Randall Munroe's open-source "Robot9000" automod bot for one of XKCD's IRC channels (where unoriginal users would be muted for N time, rather than banned).
The original post explaining it is here [1]. I'm not sure whether the 4chan implementation applied to just the 10 visible pages or all past comments.
Fun fact: Twitch also has an r9k mode for chat [2] (that scopes "unique messages" per-chat over a 10-minute rolling window).
Twitter: we're testing out a new safe word feature to address that.
They should keep this. Randomly pick a new word each day, anybody who says it gets locked for a day.