As it is now everyone is a moderator, and I think that's as it should be. It should be a decentralized network, and the problem is the centralized distribution and the shortsightedness of some of the whales. Adding more centralizing features like designated moderators with special powers is only going to make things worse because that power will ultimately still be controlled by the stakeholders, amplifying the destruction of the centralized stake distribution.

I do think there should be curation penalties as well as curation rewards. If you use your stake abusively to upvote spam or downvote in order to censor, other stakeholders should swarm and counteract those votes. Just as you should receive curation rewards for upvoting popular content, you should receive a negative curation reward (a penalty) for voting against a strong stakeholder consensus. In any case the survival of Steem depends on the majority of stake being held by good faith voters.