He can, but it requires him to access " The database ". Or whatever he refers to it as. Basically he has to go into the innerworkings of the site to mess with that stuff, but if needed to he can look at who voted on what, it's just a pain.
Because of this, ( from what I gathered ) Pokemaster isn't usually snooping around who voted on what unless it's a big situation like someone being spam voted.