This may come as a surprise, but in most western countries, to a first approximation, people can change the name they use when interacting with the state to whatever they want, whenever they want. The process does involve a small bit of tedium, but really isn't particularly onerous or expensive.
I've had multiple names over the course of my life (and notes linking them together in various documents should I ever need to prove to someone that the person with name A is the same as the person with name B; to date, I never have). It's pretty common.
Moreover, people can use whatever name they want in whatever places they want on the internet, and don't have to be obvious about it when it's not the same name they use in other places online or offline. If I tell someone my name is John Smith, 99.9% of the time all they need that information for is to know that I am the same person they interacted with previously; they don't need to know or care what my bank or my family call me, nor is there any reason for me to tell them.
I've had multiple names over the course of my life (and notes linking them together in various documents should I ever need to prove to someone that the person with name A is the same as the person with name B; to date, I never have). It's pretty common.
Moreover, people can use whatever name they want in whatever places they want on the internet, and don't have to be obvious about it when it's not the same name they use in other places online or offline. If I tell someone my name is John Smith, 99.9% of the time all they need that information for is to know that I am the same person they interacted with previously; they don't need to know or care what my bank or my family call me, nor is there any reason for me to tell them.