I find usually when feedback is left it is often too late.

And as you say, can't please some buyers whatever you do.

I wouldn't leave a response to the feedback as it only draws attention to it.

Forget it and move on.

As for a way to approach such situations in future is perhaps a professional message that is non personal.

Dear buyer,

We have noticed feedback was left for the recent transaction.

If there is anything we, as a seller can do to improve the way we conduct our business, please let us know.

Kind regards,

Buyers will either not respond, meaning they were never going to do so favourably or will contact you and probably be civil.

Good luck.