My concern is about what the chemicals that are left in the quilt might do to the fabric. Even if you can't see them, the fact that the markings come back when cold indicates there are still chemicals in the quilt even after the markings have been "erased". If the chemicals are acidic, they could be gradually eating the fabric along the marked lines.
Does anyone know if the re-appearance of lines in the cold ceases after the fabric is washed? That would indicate to me that the chemicals wash out, in which case the pens would work for me since I always wash my quilts as soon as they are finished.