The Older I Get the Less I Know

I have had a revelation! This might not seem like a lot but I am very often a social idiot, so I'm glad I've had my eyes open at least. Anyway, here goes: Manners, or ettiquite, protect us from the unpleasant consequences of faulty assumptions. Or, as my "interpersonal communications" teacher taught in high school, "When you "ass u me" you make am "ass" out of "u" and "me." Recently I had a neighbor (neighbor A) talk to me and as we spoke it became apparent that another neighbor's (neighbor B) actions or lack thereof were driving her crazy.
It's hard to condense everything into a brief version but basically the Neighbor B had assumed that Neighbor A didn't care at all if B's kids were all over the play equipment or if B's husband took it upon himself to "fix" the broken equipment so that his kids could play on it safely. After all, she assumed because no one ever said anything no one cared and because the slide hadn't been fixed right away it wasn't going to be fixed unless she did it. Or maybe I'm just assuming what B was thinking. The point is, if everyone had good manners, permission would have been asked before the equipment was played on or fixed. There were a few other issues of irritation we discussed but ultimately they all came down to assuming a person felt a certain way or had a particular motiviation which might not have even been the case. But if people had just behaved in a mannerly way--asking permission, respecting privacy, inviting others and not asking "nervy" questions, then many assumptions which are probably wrong would have never been made. So maybe I need to check out a Miss Manner's book so I can brush up on my behavior.