Twitter on Thursday adopted — and then quickly reversed — a change to the way people can block others from interacting with them on the service. The brief change set off an uproar among users who said it opened the door for abusive behavior.

Before, a blocked user could not interact with the person who blocked them, and could tell that they had been blocked. Under the short-lived change, blocked users would not know they had been blocked. They could view and send tweets to the person who blocked them, but those tweets would have been invisible to that person.

It was the latest example of a tension that Twitter, Facebook and other social networking companies face: They want to encourage more sharing and openness, yet need to protect their users’ privacy. And with a vocal user base, they are often forced to defend or roll back privacy changes.

Twitter made the change, which it announced only on a help center page, in response to requests from users who wanted to avoid abuse and retaliation by people they blocked. But people immediately and vociferously reacted online, saying the change invited more abuse and stalking because people could view and interact with the tweets of someone who blocked them.

“Twitter is no longer a safe space,” wrote Zerlina Maxwell in a Change.org petition to reverse the block that garnered 2,250 supporters in the short time the change was active. “As a public person who uses the medium for my work, I am very concerned because stalkers and abusers will now be able to keep tabs on their victims.”

In a post announcing that Twitter was reinstating the original blocking policy, Michael Sippey, a vice president of product at Twitter, wrote, “We have decided to revert the change after receiving feedback from many users – we never want to introduce features at the cost of users feeling less safe.”

He added that the current policy was “not ideal, largely due to the retaliation against blocking users by blocked users” and said that Twitter would “continue to explore features designed to protect users from abuse and prevent retaliation.”

Twitter, which has been known for its aggressive stance on free speech and freewheeling conversation, has been grappling with policing abusive tweets. In July, in response to the complaints of a woman who received rape threats on Twitter, it added a button to report abusive tweets.

Twitter explains how to block people here.