I think these events have shown that before signing up, the person owning the account must agree to simple TOS message including a mention that participating accounts will upvote 7 posts per week, but these votes may not be made evenly throughout the (defined) one week period. This seems to be the source of the controversy, and if it's made less ambiguous when someone signs up to use the service, there is less potential for controversy.
As for current users, who may not understand your terms because there were no terms presented on signup (forgive me if I'm wrong, I don't use the service), here's one suggestion on reducing confusion: Send a 0.001 STEEM transfer to all active Steemvoter users with a memo/brief message linking to a post that explicitly states the terms of the service. This way you can make a reasonable effort at clarifying terms for all existing users.
They collect email address so may easily contact the users. And I am confirmed that there is no TOS message on signup or adding account.
Sure, we can send out a reminder of our terms of service, but if the hope is that people will unsubscribe,we don't envisage many will.
They also retain keys to accounts that are not even still online.