Well, I'm buying Barnbum's Watercolor Floral Log Cabin Quilt, and I asked her to make a label for me.
I don't know if I would "sign it" literally, but I would probably make a small discrete label that said my name and the year, and hand-sew it on, rather than fuse it or anything. That way whoever bought the quilt could remove it if they wanted to, or use it to refer other buyers to me!!