This is an older thread, fun to see some of the people from back then are still on.
I'm usually pretty good about getting fabric to behave but some fold lines just do not want to come out and sometimes they are very noticeable. Next time it comes up, I think I'll try my dying heat treatment in the microwave and see how the fabric reacts to that. (Taking clean washed wet fabric, submerge in a large pyrex bowl, cover with ample water and then plastic wrap it sealed. Heat on high for 20 minutes. Carefully drain and rinse.)
Sometimes the "crease" is more of a color illusion from sun damage along the top of the bolt, there's really no crease to get out! If the fabric was folded with right sides in, that crease could even be darker after long storage from minor dye crocking.