It's true that social interactions can be smoothed if people follow the same rules.
It's also true that social interactions can be smoothed if people assume good will on the part of other people they're interacting with, rather than making up other kinds of stories about them, such as that they are trying to be insulting or superior.
(What I mean by making up stories: I think that sometimes people make assumptions about what other people intend, and sometimes the assumptions aren't entirely accurate, for one reason or another. Sometimes there's not enough information available because one doesn't know the person well enough or doesn't know everything about the specific situation that person is in at the moment. In those cases I think one has a choice about what assumptions one makes, and the choices can affect one's mood and behavior.)
For example, a person can assume that someone means well but came from another culture where the politeness rules differ. A person can educate themself about other cultures' politeness rules and then use that knowledge to refine the stories that they make up about other people's behavior.
I think it's usually easier for a person to change the stories they make up about other people than to change other people's behavior. So if a person is getting upset partly because they are making assumptions that someone else is being rude or arrogant or self-important, changing the story they're making up might help them feel less upset.
In other cases, the behavior might bother them even if they know there are possibly good-will or legitimate reasons for it. Changing the stories might not help with that.
And sometimes the evidence becomes overwhelming that a person does intend to be insulting or does feel superior, in which case assuming good will might be counterproductive.
More examples (the numbers are based on the numbers in jorm's original post):
1) When a person doesn't say "Thank you" to a compliment, they might come from a culture with different rules about compliments or might be uncomfortable about what they were complimented on. It might not be because they are feigning humility.
5) If a person corrects another person, they might come from a culture where correcting a person is a sign of respect for that person. Maybe they are not trying to show the person up up as stupid.
8) If a person shares their medical diagnosis, this might be an act of trust on their part, rather than an attempt to excuse themselves from following the rules. It might be part of an apology. Some people, when they apologize, start by explaining what led to their actions, and don't mean by the explanation that they should therefore be let off the hook for bad behavior.
9) If someone makes plans and doesn't show up, there might have been an emergency that prevented them from showing up. If someone is late, they might not be very good at estimating how much time it takes them to get somewhere.
15) If someone is sitting in the corner, maybe it's because they are disabled and that's where the host put a chair for them. Maybe it's because they are temporarily taking a break from the conversation. It's not necessarily because they think they're too important to make a social move.
18) If someone uses a calculator to figure the tip, maybe they find arithmetic difficult, or maybe they are from a culture that doesn't include tipping so they aren't used to it. It doesn't necessarily mean they are cheap.
20) If someone replies tersely to an electronic communication, they might be trying to show respect for another person's time (assuming that the person gets lots of e-mail and trying to minimize the amount of effort required to process the e-mail). They aren't necessarily being hostile.