The "harm" is that the power of moderation lies in the hands of the people who incidentally created this thing. They're probably doing it in good faith and the

The "harm" is that the power of moderation lies in the hands of the people who incidentally created this thing. They're probably doing it in good faith and the final result is reasonable, but the process of allowing creators to moderate responses of such an influential thing can be dangerous. Not that the problem is new, see eg. Google search (it apparently doesn't refuse to answer questions, but maybe they're just silently censoring "worse" things and just presenting the "less bad" things to you), Facebook/Twitter content moderation, etc.