Depending on the wood color, density, and moisture during cut, Walnut can fray giving an almost hairy appearance. This is more common with lighter boards.
There is no degradation in stability and is not an indication of splitting. It is nature and simply means the fibers are pulling more than slicing when cut. After milling, each box is heavily brushed and tweezers are used to remove most fibers. Those that persist will wear off naturally over time.
