Shreyas Doshi, Twitter’s director of product management:
Second, we have begun to test a product feature to help us identify suspected abusive Tweets and limit their reach. This feature takes into account a wide range of signals and context that frequently correlates with abuse including the age of the account itself, and the similarity of a Tweet to other content that our safety team has in the past independently determined to be abusive.
It will not affect your ability to see content that you’ve explicitly sought out, such as Tweets from accounts you follow, but instead is designed to help us limit the potential harm of abusive content.
There is something about twitter that generally brings out the absolute worst in some people.
There is a pattern to it, though, which I've always thought could be addressed at least partially through algorithms not unlike spam-filters.
I don't usually say this about Twitter, but these were good changes to their policies on harassment too.