因为微波能...内外的温度差别可能会非常大....产生有害物质?

It did not mention Extremely Low Frequency Electromagnetic waves, which is known for causing cancer of young people. This is a wave generated by the transformer insider microwave oven. Second point, normal use conditions could not be defined. We cannot exclude component interactions and extreme use conditions. Egg is just one of many possibilities. Water is not only thing that can absorb microwave. A large number of other compounds can absorb microwave. It is uncertain how fast different compounds can absorb the wave. One need look at chemical bonds and energy levels. This raises a concern whether certain compounds could absorb the wave to generate high temperature in certain localities. One real problem is such a large energy source hits a little food in a very short time. Some compounds may break up. Of course, boiling water must be safe.