I feel like in some way the shills are exploiting the framework of voat's upvoat / downvoat functions. As a new member I can only upvoat until I hit the minimum 100 comment contribution points. Maybe they have created or purchased a variety of accounts most new, allowing them to mass upvoat posts that they favour. More worrying would be them gaining control of accounts that have the minimum comment contribution points, which would allow them to mass downvoat as well.