When I first started ponding someone I knew that also had a pond asked me how I liked playing God. It was a little esoteric but after I thought about it really your fish's health is in your hands. You can give them as much food, shade, light, space, water conditions, etc that you want and see how those things manifest themselves with your fish. I don't think withholding food is necessarily cruel, but you have to think what you do affects your fish. I think in a lot of ways feeding goldfish in a pond is over rated. There are so many stories even on GPF about people stumbling across neglected ponds with large fish in them doing perfectly fine. The bottom line is I feed my fish because I like to. I don't think it's bad for someone else not to feed theirs, however it is important for fish to fatten up a little before winter so maybe some feeding is really required.