As an introvert who gets mistaken for an extrovert often, I gotta add myself to the group of folks pointing out that the assumption that introverts are shy or quiet, or avoid chatting and social settings, is just a stereotype. There are introverts who are shy and quiet!! But there are also introverts who are talkative and enjoy social interaction -- I'm one of them! I'm SUPER talkative and I love interacting with people, I'm just very tired afterwards and need time by myself to recover.
I struggled to explain this to my friends, who didn't understand ideas like "I can't hang out with you because I was just hanging out with someone yesterday and I'm socially tired," so I came up with the social energy = physical energy analogy to kind of explain it.
(And on the flip side -- there are also shy extroverts!! tbh I think Shy Extrovert and Outgoing Introvert could both be really interesting characters to explore)
I'll also point out that not everyone falls into one of these two categories. Introversion vs Extroversion is more of a sliding scale, and ambiverts are a thing that exists!! Desperately needing social interaction to recharge while also being exhausted or overwhelmed by too much of it is an experience lots of people have, that would make an equally interesting character!!
Runewriters basically has three main protagonists - Tareth, Sev, and Jonan. Severian is Extremely Extroverted in the traditional outgoing way, while Tareth and Jonan are both introverted -- but Tareth and Jonan have a difficult time understanding each other because their introversion manifests in different ways. Tareth is very shy and easily overwhelmed if she's dealing with folks she doesn't know, but genuinely likes people and wants chances to connect with them and make friends. Jonan is not shy at all -- he's not intimidated by crowds or public speaking -- but doesn't like the majority of people and doesn't enjoy opening up to others and tends to want to be left alone.
While Tareth is terrified of crowds but comfortable being close to a single friend, Jonan is the opposite.
I never really liked the moral that tends to happen a lot in stories, where the introvert has to learn to "loosen up" as the extrovert drags people into their life (Shrek and Donkey are the first example of this that come to mind). I think in reality it has to be a bit of both -- the introvert learning to reach outside of their comfort zone to meet the extrovert's needs, but also the extrovert learning to respect the barriers that the introvert needs. Compromise and communication! I think it would be cool to see more of that.