I absolutely love silk thread for hand needlework - I do blackwork embroidery with it - but the first two reasons that pop into my head to not piece with it are #1) price, and #2) washability.
I don't know how much of it you have or what weight it is, but you can go through quite a bit of thread, depending on the size of the quilt, and silk thread is not cheap. Also, it's not always colorfast and you have to be careful how you wash it.
I believe it's stronger than cotton, but not as strong as polyester, so Glide would be the better choice if that's a concern.
And silk thread is just beautiful, why hide it inside the quilt where it won't be seen?
That's my 2 cents!
