This is something I've been trying to get a decentralized social media site to implement since the original idea for Hivemind. Presumably you will implement these in custom_json?
I encourage you to add operations for both adding and removing either usernames or specific permlinks.
Distributed, opt-in moderation without gatekeeping is the goal. Nobody wants censorship, and nobody wants an unmoderated site. This allows individual end users to choose how much moderation, and by whom, they want.