Same reason we boil tea to make it hot, then add ice to make it cool, than add lemon to make it sour and then add sugar to make it sweet! Go figure! lol

I use the power level button. Usually start with, say 111, or 222 (always use same numbers in order to reduce pushing extra numbers) and then set the power level at 30%. Microwaves, on full often heats the surface first and the inside of the food is not done. Reducing the power warms things more evenly.

I don't know. Everytime I make my sock soup it turns out bad.

You under estimated the power of electromagnetic radiation.

You want to get it hot enough to kill any organisms.

Don't cook it at full power, and stop it a few times to stir it. Works for me.

Unlike pizza, whose very purpose is to burn your mouth !

Probably because you have cooked things in the microwave this way for a time, you like me want to get it hot and that is what you are supposed to do and then you let it cook so it does not burn your lips. I do the same thing. All that should be happening in the microwave is the water molecules are being excited, so they move faster, and the friction of this process heats the soup. I do not know about harming any of the various nutrients, as all that is happening is they are being heated. The same in principle is happening when you put the soup into a pan and heat it on the stove, it is just a different method. Radiation, if that is what you are worried about, here is nothing more than energy being added to the molecules of water so they will move faster and heat the soup. Works this was for everything.
Now there are microwaves that run on different energies, used in factories and such, that heat different molecules, this one can heat the plastic in trash and remove it from the rest of the garbage.

Not a bad practice to pasteurize it.