Ebay won't remove that feedback as it doesn't violate their policy. I'm not sure why you would spend literally thousands on legal representation, when the outcome is going to be the same.  Your first negative clearly didn't affect your sales, what makes you think this one will?

Most buyers don't even look at feedback. If they did, then the Chinese would be out of business real quick. Especially given they can rack up 100's and thousands a year, and people continue to buy from them.

I'd be more concerned about your reply to the feedback, than the actual comment itself.