When you see an introvert lost in thought, don’t say “What’s the matter?” or “Are you all right?”
On a more serious note, the section of the article about arrogance describes a genuine problem for us introverts. I can’t tell you the number of times people have assumed I was aloof or arrogant when, in fact, I just didn’t have anything to say or was feeling a bit overwhelmed by the number of people around. So the next time you decide that someone is arrogant not because of something they said, but because of something they didn’t, give ’em a break, OK?
Interesting addendum: many years ago I figured out the exact number of people that constitutes a “crowd” for me: six. I’m usually OK with five, but start to shut down with six. On the other hand, I love public speaking.