If it were my quilt I would be sick once I saw the mistake. I have one I quilted myself and didn't see the mistake until afterwards and it ruined the entire quilt for me, and my mistake was not as obvious as this one. Whoever made the quilt can applique over the top but would have to remove the feathers on that one block and try to duplicate the feathering once the appliqued block was on. A lot of work to fix when it could have been done so easily before quilting. The client may have made the "mistake" deliberately and all is well but, like I said, if it were my quilt I would be sick about it.