If a restricted user mentions someone who doesn't follow them, that person won't see the tweet or receive a notification about it. Retweets of abusive users from followers won't appear to people who don't follow the punished user.
"Conversations are core to Twitter, but if we detect behavior that may violate the Twitter Rules or inhibit other people's ability to express themselves freely, we may temporarily limit certain account features".
However, this new penalty box could actually go a long way towards curtailing targeted harassment, especially if these kinds of restrictions are being enacted in a timely manner.
Last week, it revealed that it would be impossible for people who have been suspended for abusive tweets to create new accounts, and the week before that, it detailed new ways for users to report abusive accounts. "We've detected some potentially abusive behavior from your account", the emails read. Twitter CEO Jack Dorsey recently said that providing users with better controls is the company's top priority, and this effort is part of that. The company has boasted about being the "free-speech wing of the free-speech party" and talked about how the service helped free Egypt during the Arab Spring.
The new protocol is already affecting users whose tweets violated the rules. For now it seems that the default timeout period is 12 hours, although Twitter may implement different lengths for different or repeat offenses. And by limiting the amount of time spent being throttled, Twitter shows users that the restriction isn't permanent. Affected accounts will only have their tweets seen by their followers until the ban is lifted. "Starting today, you won't get notified when you are added to a list".