Wow. I relate to almost everything mentioned in this thread! It's always a relief to know that there are others like me.
To add to or reinforce what's already been said:
Being able to read/understand people and situations too easily is sometimes difficult. It gets in the way of normal interaction in a way, and makes me feel almost intrusive. Sometimes when people are talking, or telling me what or why they did something, I instinctively know what they're going to say, and it can be almost frustrating because I can't just say "yeah I know". Or, I can't tell them how or why I know something. It's almost like I have to pretend to be surprised or pretend like I'm trying to process the situation.
Feeling like I'm from another planet or don't belong in this world. I can't connect with many aspects of society because I just see past/through them, and they hold no desire. It's frustrating to see people making mistakes, being shortsighted and unwise when I just don't understand how they can't see what I do. And, I don't like to assume I know best, I have no right to believe I do, so I tend to hold back. Either way, whether I am the one that is wrong or right, I feel different.
The contradictory personality - in many aspects. But mainly, my extreme introversion coupled with my extreme desire to connect with and make a differenece to people. The most important thing to me in life is people. No doubt about it. However, I don't feel I've mastered this balance yet. I'm working on it.
Oh, and the inability to express what I know/feel. I often sound very inarticulate! I guess it's the intuition, we often don't know how we know - we just know!