Earlier this week Barrett Courville and I visited a field where quite a few plants had this type of injury. It is late planted, water seeded rice. While we did not identify the specific culprit it is some sort of insect damage. Barrett visited some other fields later that showed much the same injury and found billbugs in the field. (See Fields Notes editions of April 30, 2011 and July 30, 2007). It is possible that billbugs could cause this type of injury although it is usually associated with an insect with piercing sucking mouthparts like stink bugs and leaf hoppers.
Below I used a piece of paper and a pencil to demonstrate how the injury occurs. The rolled up sheet of paper with a pencil stuck through it is to simulate the young rice leaf rolled up in the whorl. The pencil represents the piercing mouthpart of an insect. When the leaf later emerges from the whorl and unfurls the injury points form a dotted line across the blade width. This weakens the blade frequently causing it to break along that line.