I probably get about 60 - 70%) of my buyers leaving feedback but a good chunk of those are repeat buyers, some of which I've sold to for years, plus I sell in a collectible category (vintage Barbies) so many of these people have been buying here a long time and are used to feedback.
I would never message anyone to ask for feedback, as brettjet says it's not valued the way it used to be. Just offer good service (and product!) and hope for the best. The types of items you are selling, and new buyers could be part of the reason for no feedback.
I can relate to going the extra mile with no appreciation (your exampe of giving $150 shipping refund!) I've given shipping refunds to people who have bought multiple items without even asking about combined shipping and refund them and they never give feedback. Often the buyer who ask umpteen questions, ask for extra photos, etc. are ones that don't bother either. We just can't take it personally.
You may also find some people don't leave feedback right away. eBay mails out reminders to leave feedback for items getting close to 60 days, sometimes people might respond to those too. Just like the Amazon requests I get all the time to review my items....though sometimes so quick I've never even used/tried it to know.
Though I know it doesn't matter so much, I still like getting the feedback myself, who doesn't want some appreciation. It's like getting a thank you for doing something.
