Originally Posted by Maia B
It is correct that you must/should thread with the presser foot up, so that the tension discs are open. Maybe in the past it has worked for you to thread with it down because the thread has just fallen into place once you started sewing. I can see how you'd get thread tangles, poor stitch quality, and tension problems from threading with the foot down, but I personally don't understand how it would damage the machine. Not saying it won't, but I don't get how.
If I pull on the thread with the presser foot down, you can tell the machine is "fighting" it. It doesn't pull easily. That's how I know it can't be good for the machine. I think that's why they say not to thread the machine with the foot down, because the tendancy (when threading manually at least) is to thread the eye, then pull a short length of thread on through to go under the presser foot or to hold onto. Hope this made sense!