I think it's not a sign on your forehead so much as actual tangible reasons. Some things are unfortunately stereotypical. Wearing baggy clothes, being anxious and on edge (hypervigilant), quiet and shy, hiding skin and as you said the way you carry yourself. I think you should maybe ask why - ok, yes because of your abuse but break it down further. I'll do mine:
I'm anxious and on edge because I know that something bad could happen at any moment, people aren't to be trusted and as long as other people are around I am in potential danger, especially some types of people. I'm quiet and shy, partly because I'm scared of conflict, partly of drawing attention to yourself and because I distrust and fear people, I'm also incredibly socially awkward. I hide my skin because again, I don't want to draw attention to myself, because I don't want to get unwanted sexual attention - also huge amounts of self-harm scars. It's also because I spend huge amounts of time observing others closely and I'm looking for the signs of any shifts in behaviour yet also I dissociate a lot and am unaware of huge amounts, none of which anyone else can understand. I wear baggy men's clothing, again because I don't want attention especially sexual, I've also cut my hair very, very short. Lastly my jumpy behaviour at movement and noises, constant apologising for doing nothing wrong, I've very no self-esteem or sense of self-worth, and my posture consists of holding myself/curled up or arms crossed and biting my nails. Even if I dressed better, it might just seem like I'm anxious and/or shy but I can't bring myself to, I hide in clothing like armour. In all this paints a strong picture for anyone who sees me for more than a few seconds.
Maybe you should analyse what your behaviours are around others and in general and what you'd think of yourself if you met you? Does it paint a strong picture? Are there things you wish you could change (even if not now, maybe a goal for the future to work towards) such as the way you dress or posturing?
I think I would see my self as someone who had been abused very clearly but I already know that, maybe you think that people know because you'd know if you met you, but maybe they don't?