If people are self voting for ROI they'll simply create a second account to vote on the first.

Make them create the accounts, odds are pretty good they will screw up and lose a key or two. They will have to divide their sake up, with the new curation curve that would mean less over all ROI by having more accounts. That is just an excuse to do nothing about a known problem. It would mean less HP casting a vote, and make it easier for anti-spam gangs to down vote the secondary all the way to tercentenary accounts. It is much easier for a group to down vote 50,000HP than to down vote 1,000,000HP. So why make self voting easy if that is and has been a concern, do away with it, make them make as many accounts as they want/need to get the same ROI as one single vote. Force them to dilute their power.

Most of all we need to Fix the primary cause that got us here, and prevent it from happening again.