This is interesting. I got to searching the global login system for 91.12.* IP's and here's what I found. The two highlighted values are the two ip's under which the ZGH was detected:
91.12.47.214 = p5B0C2FD6.dip0.t-ipconnect.de
91.12.36.37 = p5B0C2425.dip0.t-ipconnect.de
Note that the IP's are stored in decimal format. Clearly he's abusing the registration system to get certain id's. Stealing names, registering multiple accounts, and cheating. Not looking good for Agent. Looks like I need to disable registrations with mailinator as well.