Monofilament thread is like the wash or don't wash question. Quilters will never all agree on either one. Some people hate monofilament thread and you will never change their minds. Some people love it and you will never change their minds.
I love it. It has never melted and I've washed quilts that have appliques done with it several times and all is well. If it's good enough for Eleanor Burns it's good enough for me.