Per the feedback rules:
Feedback Removal/Change Rules
If a dispute is opened and resolved, the negative feedback will be changed to neutral and the comment will be updated to reflect the issue has been resolved.
Feedback based on rudeness or slow service (non-extreme) can only be neutral, not negative.
Feedback can only be removed if it's false.
If you believe feedback is false, you can open a dispute thread.
False feedback must been reported within 30 days
After 30 days, the burden of proof falls solely on the member who received the feedback.
Example: Joe gets a negative feedback from Roger. Two months later Joe disputes the feedback. Joe must show proof the feedback is false. Roger does not need to prove his feedback is true.
You have to be able to prove that it is fake.