ditto to all you have said!
I've had the same dilemma ... I don't like taking risks and do not wash my quilts after quilting!
After reading about them here, I got a ceramic pencil this summer. It's a mechanical lead, in both black/charcoal and white.
So far so good, for the limited use I have had ... it makes a fine line, seems to "stick" when moving the quilt around, and pretty much disappears with the quilting. Or is it covered by the thread? Regardless, removal has not been an issue, so far!
It is water soluble, and while I have not had the need (yet!) ... some posters reported on here that they spritz it with water and rub it out, without washing. Another said she dabbed water on with a paint brush to remove the markings.
So long as it keeps on this way ... you can call me happy!