Hey Peter, I have a 17 year old down jacket (it's a Marmot, but same construction as Patagonia) and it has a few repairs that are over 10 years old and still holding strong. Aesthetically, I believe the best fix is to buy some Tenacious Tape, which is made by Gear Aid, and cut a patch that has rounded corners and extends past the tear 1/4-1/2 inch past the tear in all directions. It is applied like a sticker (peel the backing off and smooth it on the fabric) and comes in a variety of colors including clear. I like to choose a different color tape that is complimentary to the color of my jacket for repairs, but if you want to preserve the original look of the jacket, then use a matching color or clear tape. To make the repair extra bomber, brush on a thin coat of Seam Grip (silicon nylon repair goo) around the edge of the tape. It's rad that you're interested in repair. This is cheap, easy, works well, and looks remarkably good.