I'm also a frixion pen fan. I suppose I would tell the recipient if the quilt ever got left in a cold car and the marks came back, to take an iron to it, and they'll go away again. I was at a show last weekend and the woman said the ink washed out when she washed w/ water & detergent.
I will say that if i can use a regular #2 pencil if the fabric is such that I can see it...