Why is Using Distilled Water in a Coffee Maker Not Recommended?

KitchenAid^® does not recommend distilled water because of issues with the flow rate through the coffee grounds.  Because distilled water is such a good solvent, it causes the coffee grounds to swell, and slow the flow of water. This leads to bitter, over-extracted coffee or possible brew basket overflow. It is even worse with de-caffeinated coffee. Distilled water also causes the metal brewing element to slowly deteriorate the hot water tube, causing premature failure of the coffee-maker.