I've had pretty much the same thing happen to me. I left a negative trust on a similar impostor (probably the same guy operating all these impostor accounts) using my main account and received the following PM shortly after:
Kiss your account goodbye.
I am about the neg the shit out of it over the next few months with everything from newbie to sr. member accounts.
Through enough shit and some sticks.
Should have kept your fuckin nose out.
Nothing ever came from it though, so I wouldn't worry about it. Just report the message and it'll be dealt with it.