I get misremembering someone, but to switch them to a polar opposite is just... odd.

They thought your compliments were sarcastic insults. "Nice shoes you got there! Did you steal 'em off a dead hobo at the morgue?" See how that could backfire?

Are you sure about that?

I had no idea that people from my Highschool thought I was both popular and stuck up until I ran into a classmate on my college campus that told me about it …I never talked to anyone because I always had my nose in a book and was too shy to make friends. High school is a weird place for everyone. Don’t take it personally.

You realize that if several of your former classmates say you were a bully or a jerk - Then you probably were. Think carefully, were you harsh and insensitive in the remarks you made to others? If you were , think it through and apologize to anyone you may have wronged. One thing I have learned is that sometimes our memories of what kind of person we were do not always match the facts. There is still the possibility that your former classmates either have mistakenly who you are or they just didn’t like you for some reason unrelated to what you did or said. People can be misunderstood - I remember one girl in Junior High calling me “stuck up” because I apparently wasn’t paying attention to her attempt to get my attention. I was shy around girls at the time and was a nerd long before it was “popular”. At the time I was far more interested in SciFi books and my other hobbies and interests. Since I do not recall hearing that from another person and don’t recall actually treating that person negatively, I assume my shyness and interest in books and other things was simply misinterpreted. But if multiple people had told me that, I would have to figure out if I might have been rude and apologize. In my High School there was a college preparatory track and one for everyone else. Except for PE and shop there were no classes containing both the college prep track and the other track. So my personal High School experience was spent mostly with other somewhat “nerdy” or high achieving students and things like that came up much less often. Let me give you the “man rule” I learned long ago - “When in doubt apologize.” It costs you little and makes life easier. To apologize - (1) Acknowledge what you did without any excuses. (2) Say you are sorry and wish you had not done that. (3) Say you will try to not do that again. Don’t let your arguments spill over into your apology trying to “explain” why you did what you did or said - If you do that it will spoil the apology.