Something I think would serve this forum well... Let's say Member X signs up as a new member today, right now, with a join date of September 14 2012 at 9:30 PM. If an entire year goes by with 0 posts until the date that the administration wishes to employ, six months or one full year, September 14 2013 at 9:30 PM, then have the system automatically delete the account and add the IP address to a recognizition database to block any further registrations from the same address.
As far as fellow members you feel are braking forum rules annoyingly, I understand your not wanting to divulge the members' name privately. However, perhaps contacting us staff members in a private conversation would be best, as I like CaseytheMuppet am unclear as to whom you may refer.