Facades, communication and how well we really know each other

When I was in college, I worked on a paint crew painting dorms all summer. When you are painting, there is a lot of freed up mental space to talk and think about things. One summer, my boss, Milton, introduced me to a theory he called the "mirror theory." It's not revolutionary, but it has stuck with me. The theory basically is this: the way you feel about someone else is the way they feel about you. My immediate reaction to this information was, "S***! They know that I don't like them!?"

Special cases aside, people are usually "nice" to each other. "I like your shoes," "How was your weekend," "How have you been," and similar comments, are shared between casual friends and coworkers all the time. Assuming we know how our close friends feel about us- what about everyone else? Are these comments sincere, or are they just a convenient cover up for calculated animosity? Don't tell me you don't care, because even if you're like me and say that, you still do a little. Do people I am nice to but don't like, feel and act the same way towards me? I mean, it's fine if I secretly don't like someone, but for them to feel that way about me when I'm being perfectly fakely nice is outrageous.

Ever find yourself secretly disliking someone (to varying degrees) one second, until they say something to you like "Nice shoes!" and you like them again? Are they just playing nice too by using tried and true expressions to "listen" to and "flatter" you? If they are, that's infuriating. Only I am allowed to do that because obviously noone has any reasons to dislike me (whereas people who I dislike clearly I have reasons to dislike, such as, they're mean). I've written posts before about people not saying what they mean and being tactful, etc, and beaten that subject to death, I feel. However, as one of the most sarcastic and skeptical person of others I know (until I get to know them, of course), can even I be fooled by someone who secretly doesn't like me?

Friction exists, even between people who are perfectly nice to each other, just because their personalities are different. Do we ingest this and magnify it to the point where we take it personally that someone could dislike us for "no reason"? I mean really, what's the big deal when statistically it's just gonna happen? Why can't we just fake it to fool the friction?