Personality types and introversion recently came up on one of the online boards I comment, which
From what I've observed, introverts assume that boundaries should be in place unless otherwise specified, whereas extroverts are more likely to assume the opposite. Consequently, while an extrovert would assume it is neighborly to drop in on someone, an introvert would rarely do so unless s/he is expressly invited to come at a particular time. That doesn't mean the introvert doesn't like his/her neighbor but that the assumption is that people want to be left alone unless they tell you otherwise.
Now to get to the particular incident of different assumptions of what constitutes polite behavior, here's the example. I had a friend who stayed in the empty house of a neighbor of a relative once. Said relative told me afterward that the friend was shocked at what the friend did. I was imagining all sorts of horrific scenarios and then was told that the really shocking thing was this: the friend did not pick up the mail that was put through the door slot. Now if you're an introvert, your assumption of boundaries would tell you to leave as much of someone else's stuff alone as possible. That would extend to handling someone else's mail that just happened to be delivered through the door. It takes an extroverted mindset to assume that showing such respect for someone else's privacy is a lack of courtesy.
I'm now adding one other example about circumspection with respect to boundaries, as it just happened. I commented on someone's post and referred to a Talmudic story to make my point. Someone else said I was misrepresenting it and said I got the name wrong. In truth, I would do the same, but only if I were 100% sure that the other person got it wrong.In this case, the name I had written was correct. I ascertained it again for myself by getting out the primary source. When I pointed that out, the woman who had disagreed with me had to concede that point and then made excuses for herself that she had just been on a long flight, etc., etc. I understand making mistakes when tired. I do that myself and have even been guilty of making typos I would normally spot. However, I would not ever challenge someone on the basis of at hazy recollection, and then say, well, what do you want from me, I was tired.. That's also part of introversion: being very prepared and very sure before speaking up, particularly when publicly contradicting someone.