Hi!
About this topic. I sent a Ticket to Gw2 asking if it was possible to change for ‘own reasons’. They told me this:
“I would like you to know there are issues with Display Name Change. For example: Players may experience broken guild lists, broken guild rosters, inability to chat, broken friend/block/social lists, and having both the old and new display name visible. It’s not offered to change a display name.”
As they said, it’s not offered. Though a friend of me still changed her Display Name. I wonder why not others too ~ It kind of made me quit playing Gw2…