Thanks for your opinions, everyone. Like I said, I'm not necessarily discussing a specific transaction, more looking for standards and stories of when others have chosen to leave neutral or negative feedback for buyers, to see what the range of opinion is out there. I think I'm getting a clearer handle on what my own standards are, but I'm interested to hear what others think and do.
The fear of getting retaliatory negative or neutral feedback is always problematic. I often wait to give feedback to buyers until they've contacted me or left their own feedback for me, just in case there turns out to be an issue for me to fix before they're completely satisfied. I feel I can't really be sure they're satisfied (and the experience has been "positive" for both of us) until I hear back from them.
In terms of my own store, the frames are not a problem that needs solving; I've only had one time when the secondhand frames caused any sort of issue. Like I said, I make sure to contact people and even send photos of possible frames, which are no cost to the buyer, and my customers really love that. It's eco-friendly, economical for me AND the buyer, and it's optional -- my policies and relevant listings state they can opt out of the free frame if they choose. It also allows me to keep a variety of frames on hand for all types of requests, color schemes, and for the variety of cross stitches in my shop, which are different enough from each other that they really benefit from multiple options.
The recurring theme in my shop is that people are pleased with the variety and eco-friendly option.
In the particular case where the frame caused an issue, it WAS actually the exact frame pictured in my photographs that I sent, so I do not believe that would have solved the issue.
(And yes, Nicole, exactly! That's a great template for a comment, and similar to my follow-up email, which was much longer (lol, you can tell I write a lot!), but equally diplomatic, and I made sure to kindly point out the spots where I'd stated my frame policies and the fact that the frame was in fact the exact one pictured and was also free...etc. I was hoping to be able to get some personal interaction about that particular situation from that, but I've stopped expecting it as that was over a week ago.)