Could you perhaps talk to the people who posted the feedback and ask them to get it removed? Cause I mean there's no point to it knowing that the previous owner no longer owns the account.
I have asked them and and they were neutral about it and I did not force the issue. The account may get more -ve feedback so I decided to sell with the -ve and the buyer can try to get it removed. The price reflects the -ve status.
I have posted using that account and a signed message from one of my addresses.