Deffo call ebay, speak to a sympathetic person. Explain what has happened and they will remove the comment. Make sure you throw in he has left you vindictive feedback as he wanted to pull out the transaction etc etc - get some sympathy by mentioning your otherwise top selling record. They can read the exchange of messages between you and 'prowanker ebayer' as they have access and can judge who was being a Cnut about things. 100% they will remove.
'B' is a fucking good idea too. Top man.