Activity and loyalty can get you elder but shouldnt get you co. There should be a huge level of social commitment before you trust the person enough for co, even then you could get duped but its up to you if you think the person should be one. Co-leader isnt something you give as a reward or something, its a functional role that should be given for a reason. In this case it sounds like your fault, if someone spent a good few months in your clan and spent all that time lying and pretending to be someone else and you promoted him then in that case it may not be entirely your fault.

