On social networks, when your account is public, anyone can “follow” you and therefore see everything you post or comment on. That’s the principle.
But there you are, there are people we don’t like, for a whole lot of reasons. On Twitter, it is possible to hide them so that they no longer see their comments and even block them so that they cannot see your comments or react either.
The service is trying a new approach by allowing a person to be removed from their list of followers. Thus, they are neither hidden nor blocked, but they no longer follow your posts. An intermediate approach, gentler (but nevertheless annoying for the person concerned), which we will see if it proves its worth.
For the moment it is only a test, proposed on the web version.