A New Type of Leaf Screen?
This gutter may be very effective at separating leaves from the water off the roof, but only at the expense of water running down the side of the house and causing damage. This pattern of deterioration is certainly unusual – I would suspect that it may be corrosion from some type of de-icer chemical/pellets or possibly seeds that collected in the gutters and decomposed. Or perhaps the holes were made by a person for some misguided purpose. Regardless of the cause, this gutter is beyond repair and should be fully replaced.