Valerie Peter recalled that, after she followed a bunch of astrology-focussed accounts on Twitter, her feed began recommending a deluge of astrological content. Her interest in the subject quickly faded—“I began fearing for my life every time Mercury was in retrograde,” she said—but Twitter kept pushing related content. The site has a button that users can hit to signal that they are “Not interested in this Tweet,” appended with a sad-face emoji, but when Peter tried it she found that Twitter’s suggested alternatives were astrology-related, too.