As an additional bit of information...... forum software frequently USED to have a name change feature. Nerd alert: while the username field should be unique, it probably isn't the primary key. As such, users could change their names fairly easily in a lot of environments. By observation, I did see the aftermath of such shenanigans, and it resulted in that feature being disabled when the board owners came down hard on the miscreants for causing seventeen different kinds of problems. I've been out of that world but I'd be hard pressed to figure out any board application that supports name changes by the users directly. Or at least, an enabled feature.
Most people would be rather surprised to find out that they're really far less anonymous online than they think, and it's all in little dribbles and drabbles of info.