Oh dear OP, this happened to a friend of mine a few years ago and she was so upset. Although it was ‘anonymous’ in the sense of her username wasn’t identifiable the content of the post was quite outing.
When I post now I am very careful about what I say just in case something similar happens to me.
For example if I want to write a post about my 18 year old niece who lives in Wales who has just got a new job as a chef and her boss is trying to fire her for refusing to work weekends, I will change it to being concerned about a 26 year old nephew who has just moved to London who has got a new job in an opticians and they want to fire him because is refusing to work Mondays and Tuesdays.
So the scenario/problem remains the same but any kind of identifying details are almost the exact opposite of the reality.
So as a general rule I change the sexes, ages, locations and careers (if applicable) of the people in my post, and usually how I know or where I met them too etc.
Plus if you take a look at my username…. I don’t live in London and I wasn’t born in 1980 either 🤣
Maybe I’m not even a lady 🤷♀️
Between misleading usernames and lots of changed details in my posts I like to think that if any of my posts did end up on another social media platform I (or whoever I’m writing about) wouldn’t be recognised.
Keep as much of your reality as hidden as possible!