IMG source - CloverChronicle.com
"...a secret ballot is hard if not impossible to implement on a blockchain..."
Create a hash when the vote is cast, and publicly verify the hash while not linking it to the voter. Seems trivially easy to me.
Regardless of the potential of secret ballots, I note this seems to explain Steem's witness structure well.
Thanks!
RE: How Vote Incentivization Monopolizes Delegated Proof of Stake