A. Joker did refer to himself as "Wang" in Gaiden Vol.2, but soon after joining the 12th unit that Geddoe was in he changed it to the present Joker name. The rest of the unit other than Geddoe actually uses a disguise name as well. The names Ace, Queen, Jacques (Jack), and Joker are all based on playing cards. They do not prefer to reveal their true name because so many carry memories of various fateful events in their past and as Harmonian mercenaries who are sent on top secret missions, they do not want their identities to be known . These names are some what like a code name among the mercenaries. This change is not required and it is not a problem to go by your real name, but it's possible that Aila may be called "Heart" in the future.