Read the quote again. I said lack of electrolytes is harmful, because that's what you asked. I don't believe that distilled water is harmful by itself (though if you take it and you don't know that you need to take in minerals from other sources then it could be harmful purely through negligence). I'm just trying to answer your question.
> But since I just found out today that the entire Navy provides only distilled water to it's sailors. (think 3 months under the sea in a submarine with only distilled water)
But sailors are also given vitamin supplements (to prevent scurvy and a variety of other diseases). I'd be surprised if they aren't also given some form of mineral and electrolyte supplements, to combat those problems. I don't know why they'd provide them distilled water though.
> A commenter further down says distilled water causes stomach cells to explode and diarrhoea.
I'm in agreement with you that this comment doesn't make any sense.