Feeding prior to any disturbance in the tank, which a water change may be, is certainly not good for the fish. Comparable to humans being told not to exercise for 2 hours after a meal. Same principle involved. The fish after eating have to digest the food properly, and this takes considerable energy and several physiological processes are involved. They should be left in peace so everything functions as it should.
Feeding after the W/C is up to you. I don't because some of my fish are not settled enough to eat, and the food would be wasted or if they eat there could be issues like those above. Other fish seem to love the W/C as someone mentioned so there would presumably be no issue. But as it is fine to let fish go a day without food, it is easiest to make that the W/C day to avoid possible problems.
One should never feed fish if you plan on netting them out and moving them. While part of this is the excrement in the container water, there is also the same physiological issue as above.
Byron.