Social anxiety has something in common with paranoia and schizophrenia. Your detectors are at full volume. You pick up on little signals that everyone else either can't see at all, doesn't notice, or chooses to ignore. Sometimes, these tell you useful, verifiable tidbits. Other times, you're just too high-strung, and you're picking up noise and reading it like tea leaves, seeing faces in the clouds.
There have been many times in my life when I've had an active imagination about what groups of people were saying about me to each other. Mostly it's a type of daydreaming, reflection, introspection, and brainstorming. It gives me ideas, both about the people and about what I could do to clarify things.
There are times I get delusions of self-reference - my mind interprets all kinds of little things as about me - people reacting to me, instead of to themselves or the environment - little details in my surroundings that feel like they were hidden there by a diety for me to pick up on and read as personalized messages and warnings.
I recognize that these mental states can verge on psychosis. But generally I know the difference between what I actually know, and what I only hypothesize, suspect, or fear. It can be very difficult to tell the difference sometimes, believe me. But all mental health professionals I've talked to have called my reality check "excellent."
One natural strength I get from social anxiety is reading people. That's something I've relied on in my tutoring work. And I've noticed something - I want to say this in a humble way, as it is decidedly not about me - but at almost every tutoring center I've worked at, the top tutor there had obvious social anxiety. We often have a superpower for reading people and understanding. Even if we don't know how to respond (we could be very anxious), we're often very good at picking up on little clues about how you feel and what you think. This isn't just a personal theory or an observation about coworkers - psychologists have found it true.
Social anxiety and empathy are positively correlated on an emotional level, as well.
Another strength is that I'm very, very often running through possible conversations in my head. The easiest aspect of fiction for me to write is the dialogue. For me, writing a story means writing conversations between people, then filling in settings and actions. When I start writing dialogue, it writes itself. And I've gotten nice compliments on the realism.
I recognize that I write too much, and sometimes in a one-track or overly diffuse and hard to understand way, on social media. And I'm constantly acutely embarrased by it. Or ashamed, humiliated, worried, sometimes downright exhausted by all this. But... after all my efforts to be more normal, I feel like this is just kind of how I am and I hope people get it, and that I'm absolutely not trying to be jerk. The more words I type your way, the more that's a compliment... even if it doesn't seem to be.
Insecurity often has components of mental illness, or just not being quite normal. To hold everyone to the standard that we should all be equally confident, and be judged on how well we manage that - that is not good social or cultural policy in the end, I think.
I feel like talking about this today because I don't think public awareness of social anxiety is nearly as advanced as it is for introversion.