many people's inability to distinguish terseness from impoliteness That's exactly it, though. Politeness and terseness are often diametrically opposed in our s

many people's inability to distinguish terseness from impoliteness That's exactly it, though. Politeness and terseness are often diametrically opposed in our society, and since there is no standard of politeness outside what society finds to be "polite", I'm not sure how you can say many people have an inability to distinguish. If you email a long question to someone and they respond with "No.", many people would find this to be impolite or downright rude. It might be the most efficient thing and the hacker-type might think it's OK, but if most people think it's impolite, it is.