Recently, at a quilting class at the senior center, I noticed that every woman that was sewing strips together on a machine, had matched the strips and the pieces and kept them in place with a pin. The pins were placed in the seams of the two strips.
Next, as I observed, they placed the strips on the machines and began sewing a 1/4 inch seam. When they came to the pins, instead of pulling them out, they sewed right over the top of them. After the two strip were sewed together, they removed the pins and had each corner of the stripped squares matching perfectly.
I was always told to removed the pins before you ran them through the needle. I was under the impression that if you sewed over the pins and the needle struck one of the pins that you could damage the machine or at least break a needle.