Can a validator have a vote account as a PDA? Does a validator have to do anything special to do this?
The vote program supports initializing an account using
create_account_with seed and there is no specific check preventing a PDA. So a vote account address can be a PDA. However, since "The address of a vote account is never needed to sign any transactions, but is just used to look up the account information.", there isn't anything that can be done signing with this account after initialization.