Downvoting is predicated on the existence of a community that ostensibly shares some common interest or set of values. Twitter is more of a melting pot. A naive

Downvoting is predicated on the existence of a community that ostensibly shares some common interest or set of values. Twitter is more of a melting pot. A naive downvoting system can't work on twitter because tweets are designed to "leak" out into other communities. In fact, people often get the most engagement from their critics. You can't have a community about, say, fast cars that leaks into an anti-car community that's allowed to downvote all pro-car sentiments.