IF they allow VPN then banning is just useless.
But they are probably into cost cutting and just continue to ban the IP of the listed countries instead of hiring moderators. The spam still is there even after banning, you still can read the whole sentences of some posters which doesn't really make sense, not eve related to what OP is talking.
Then start thier own campaign that they can choose promoters like what they do here when they start a signature campaign.
It will lessen the cost they need to pay to all .