Well yea, obviously. But you cannot simply place the blame on the distilled water for causing the calcium/mineral build up inside a rad or wherever in the cooling system. When in fact, distilled water is supposed to be rid of its contents like chlorine, there is studies show that it can in fact remain after distillation. The coolant itself is far more of a culprit drawing these deposits from the 50/50 mixture or the water in the coolant. It would only be logical to address this as the greater cause. Its also been said that a thorough flush and rad clean along with thermostat replacing at most every 24 months should curb this phenomenon. The long term calcium and deposit build up is more rare than it is popular if proper maintenance is done. Good to see this point about the calcium build up though because it is an issue related to the coolant system albeit more of a minor one that could turn into a major problem with neglect.

Also regarding the distilled water as a magnet thing, it is true, but I wouldnt say filtered water is tthe opposition either because it could have or cause the same problems, over time. Its not like you run either water once through your system you are going to magically have all of this build up. It is simply bad practice to commonly use the water as part of routine maintenance. Proper by the book or above maintenance should be stopping or even preventing this from happening at all. Again points back to the neglect thing.

-Poss