One neat feature Google+ had back in the day were user-defined "Circles" - basically lists of people you followed _and could share with others_. So basically people could define lists with "These people talk a lot about science", "these people share amazing photography" and so forth.
And then they could post these Circles to their timeline, and others could follow all these users with a single click.
Is there a downside for implementing this feature for the #Fediverse ?