I've probably spotted many multi account.
I've spotted them a month ago but now it's pretty clear after what happened today.
5 cities were upgraded within 5 minutes of what I think are bots, all new accounts, they played the following day. And now non of them played for a day.
I scouted them multiple times, a few weeks ago, they all had exactly 500 Legionnaires.
So the question is, how do you at least report them ?