Perhaps a hardfork which changes the formula for rewards to include some kind of monthly/weekly gradated bonus for 'good behaviour' might help. Of course, coming to a consensus on the definition of this would be a challenge, but it could include metrics describing how well your votes/flags are dispersed (spread of accounts, account reputations, vests, etc.), and how many flags you sacrifice your voting power to do for example.

Maybe we could even use machine learning to establish the ways 'good accounts' comment/vote, and score all accounts for the reward share on that basis. I might be getting into fantasy land here though! :)