When I first signed up for forums, decades ago, I used my username from computer sign-ins. Eventually, it dawned on me that using something close to your real name has drawbacks.
More recently, I looked in on my old University Cycling Club, and signed up just to say hello from an old-timer. After looking at pictures of fit young riders heading off on all sorts of events, I started using this one...
We had a brief chat about the club's history being longer than they knew, and then I left them to it.