Under the short-lived change on Thursday, a blocked Twitter user could view or tweet at the person who blocked him or her, but that activity would have been rendered invisible to the victim as if the offending account did not exist. Under the re-instated policy, users could prevent their harassers from following them or interacting with their tweets. Users are also explicitly notified if they are blocked.
Twitter thought that the change was meant to protect victims of harassment who wanted to filter out abusive messages but feared that the act of blocking a user would prompt retaliation.
Vice president of product Michael Sippey wrote in a blog post that the change was rolled back after complaints. It was not intended to introduce features at the cost of users feeling unsafe.