I think we are witnessing two different series of events.
1. Bruno made a plead, just before he died.
2. His account was sold/hacked.
The way I see it, the hacker/buyer waited for the funds to be moved by Bruno's family, to start posting using Bruno's Cage account.
If that hypothesis is correct, then the imposter will never be able to sign anything from the plead donation address.
1. Bruno made a plead, just before he died.
2. His account was sold/hacked.
The way I see it, the hacker/buyer waited for the funds to be moved by Bruno's family, to start posting using Bruno's Cage account.
If that hypothesis is correct, then the imposter will never be able to sign anything from the plead donation address.
Or the person who made that donation thread was whoever Bruno sold or gave the account to. That would be the more likely situation in my opinion.
I just don't understand why the account was hacked in a short time 
It probably wasn't hacked. Just think of how much of a coincidence it is that your account would get hacked very shortly after you die. Why wasn't it hacked whilst he was alive? Accounts don't magically become easy to hack once someone has died. He'd sold or attempted to sell his accounts before so it's not surprising that this happened. Hopefully the person in charge of the account will fill us in on what happened since the account is ruined now anyway.