Is there anything that can be done?, I can only assume there will be more to come.
/quote]

Nope, if this person only created these accounts just to give you a negative feedback there is really nothing left you can do with it. These accounts are inactive now and they are the only ones who can remove the feedback they have written to you, admins and mods don't even remove retaliatory feedbacks. Listen to what they have said and just ignore those untrusted negative feedbacks since they don't even show by default in your account the feedback they given don't even have a good reference on why they have given a negative feedback to you.