The subjective way of blacklisting people may not be a good idea, since it can be used for censorship of ideas. Fans of a platform may downvote people who bring up problems concerning the interface, like security issues and such, resulting in broken system.
Or people who bring up issues about certain genetic experiments or social credit systems might be considered dangerous etc. The governments have used pedophilia as a scapegoat for surveillance and censorship for a long time, it might happen in blockchains too.
There is no reason to give up freedoms for the sake of perceived security, especially at these times of dualism and strong narratives by totalitarian medias and governments. First it is the pedos, then it can be anything.
Personal responsibility and understanding freedom is really taken a toll. Tere are already some bots spamming warnings about content a few people are not fond of, which takes away the enjoyment of sharing information.