I love mine and they make the smoothest mark and make back tracing on my applique so much easier.
I tested the ink on my high count batiks and on a cheap piece of fabric and had great results with the ink coming off on both. I did the heat removal then froze it and the ink came back, then I washed it with All detergent and back to the freezer they went and nothing re appeared.
So I think it depends on the fabric and would test each piece before using them on all of them.