It sounds to me like you are confusing Invisifil thread which is a 100wt polyester thread with monofiliment thread also referred to as Invisible thread, these products are usually nylon but superior does make a poly called Monopoly which I use quite often for ditching. I also use FilTec's essence which is nylon. Both are super fine but I only use the monofiliments for ditching. I will use Invisifil for ditching and FMQ quilting.
Invisifil made by Wonderfil
http://redrockthreads.com/wonderfil-...FceIswod4q0PhQ quilts out very much like silk. I don't use it in the bobbin as I am a dedicated user of magnaglide prewound bobbins but I do use it in the top a lot. I use it when doing dense back fills or when I don't want the thread to show, just the texture.
I do use it in my longarm with absolutely no issues what so ever. Here are links to pictures I have posted of several quilting jobs where I used Invisifil.
http://www.quiltingboard.com/picture...t-t221823.html
http://www.quiltingboard.com/picture...c-t260633.html
http://www.quiltingboard.com/picture...g-t256886.html
http://www.quiltingboard.com/picture...c-t265846.html