I agree very strongly with the sentiment of the article, and would like to add that I think the flipped side of the "I don't understand" is just as important.

I.e., You're trying to explain something and someone doesn't understand, you should be patient with the person. I don't think it's always (or even greater than 50%) the case, but enough times after finding out what the lynchpin of understanding was there are ways I could have improved my first explanation.