True, throwaway accounts are an idea. However, I believe the reputation system might influence the ability to make fresh accounts for this purpose. Also, it does cost the Steemit platform operators money to create new accounts and burdens account creation, which could be a factor if many accounts are needed. Plus, we'd still need people willing to forego their own voting power to delegate for downvoting, not upvoting.

I was thinking perhaps a system where you get 1 free downvote per day that does not use voting power. Obviously that's a rough, off-the-cuff idea, but I think we need something that doesn't make people choose between "upvote myself for 100%, or another creator I like, or punish an over-rewarded post".

It's hard to make that latter case in rational game-theory. You don't make friends around here with negativity (or too much realism, if you aren't very careful).