I think there’s a thin line between the two. What’s the difference?
In my humble opinion it has a lot to do with perception. Because I know many people who I thought who were really insightful and knowledgable, while others thought they were know-it-alls, and vice-versa. I’m not including “think they know-it-alls”. I’m talking about people who speak the truth. If people like the knowledgable person, they will be considered as smart or insightful. If they dislike the knowledgable person, then they will be considered as just a know-it-all.
It’s a matter of idiom. “Know-it-all” carries a negative connotation. People tend not to describe people they like in a negative way, so they say something else.
It used to be uncool to be a nerd. Then it became cool. Now it’s okay to call people nerds, particularly hot women.
I wouldn’t consider the words to be at all synonomous. A “know-it-all” is a show-off; they’re the ones who answer every question in class to show how brilliant they are(and I’m quite hypocritical to be critizing them). An insightful person, on the other hand, has insight. They’re able to make penetrating comments and analysis. It’s similar to the difference between knowledge and wisdom, really.
I think one of the distinctions is that an insightful person will answer a question succinctly, while a know-it-all will use the opportunity to show off how much they know about the subject and just droll on and on well past the point of anyone caring.
I remember when I was in high school and for some reason at a family party, we were discussing how big states were and my uncle said something about Maine being a real big state, probably bigger than Pennsylvania, and about the size of the Western states, Oregon, Wyoming, etc. He hadn’t been out of Maine much in his life.
The “know-it-all” in this situation says, “oh, my god, no way. Maine’s not even close. Probably every state you can name that’s west of Indiana is bigger than Maine, and also New York, Pennsylvania, and several more. Maine’s not even close. I’d bet you a million dollars Maine is smaller than Pennsylvania.”
I got a talk from my old man after that get together about really showing up my uncle. That wasn’t my intention, but that was just sort of my manner.
I think that getting away from that starts with two things:
Sometimes just not even caring that people are saying wrong things. Just let it slide.
If you want to say something, choose at least a more humble line that lets a guy save face, “ooo, I don’t think Maine’s that big. It’s big for New England, and I could be wrong, but some of those other states are on a different scale. We could probably look it up if we cared enough.”