I would certainly hope that if a customer where not happy with one of my knives, that he would let me know. I agree with the others...I DO NOT want one of my pieces floating around out there that shouldn't be. My policy is that if the customer is not 100% pleased, then I am not.
Something I do, is offer a 7-day "review" period on most all of my pieces. Once the customer receives it, they have seven calendar days to accept or decline the knife. If they choose, they may return the knife to me (in good condition) and I simply put their payment in an envelope and send it back to them. This policy does not apply to highly customized pieces that would not otherwise be readily re-sellable, but I make that clear to the customer before the project is ever started. After the 7-day inspection period has ended, my normal warranty applies....I will repair/replace any honest failure, and do all I can to make it right for the customer.
We are all human, and we do make mistakes/errors. However, that being said, I have witnessed several pieces from what most consider world class makers, that I would have been embarrassed to offer when I was a JS.
Thats the tough part about attaining a high standard....you MUST always meet or exceed that standard, and some makers will let things "slip" a little and try to get by on their reputation....which is a bad thing for all of us.
I personally think an individual maker who does such a thing should be "called on the carpet" by their customer(s). You don't have to be mean or rude, and if the maker has the "right" attitude, simply telling them what you are/were disappointed in about the knife SHOULD scare the heck out of them. If you get attitude or excuses, then thats not a maker you want to be dealing with.
As I often tell my students.... A good reputation is the most difficult thing to achieve, and the easiest thing to loose if you don't pay attention.