On hard material and when overloaded, they will chip in large, unfixable chunks.

On softer material, they continuously sharpen their edges at a microscopic scale, fracturing away tiny chips as they're worn, to new glassy ceramic molecular edges. A well used ceramic blade becomes micro-serrated.

This sounds fantastic until you think about what is happening to the shards of hard glassy ceramic which briefly become part of your food before becoming part of your gastrointestinal tract.