I don't even bother asking buyers to leave feedback any more ...
I used to do that and someone left an upsetting comment about my being just a so-so seller (she did give me a positive, but still...!)
I don't leave feedback for buyers who haven't left me feedback. I've never gotten a bad feedback after doing it, but it does leave a seller vulnerable.
I never leave negative feedback. I have before and immediately got it right back. We ended up retracting our feedback, but it was a big hassle.
If I'm not pleased, I just tell the seller or buyer offering a solution. If they ask me to leave feedback, I simply ignore.
I don't communicate outside of ebay for security reasons & ability to have evidence should I ever need to file a complaint. I try to remember to block my email address.