Fiverr should allow for the option to change usernames. If you’re only limited to one name change, that would be fine to be honest. I think this is important because I am sure a lot of sellers/buyers have names that they cant say they really associate themselves with, whether its something along the lines of a name they made when they were younger or they just simply wanting to re-brand.
And I think its evident that this is necessary due to how one of the reasons listed for deactivating your account is to change your username! If this is the case, why is it that a seller has to lose all of their reputation and hard work just so then they can change their display name? If its listed as one of the reasons why you’re deactivating, it must mean that there is a significant number of people deactivating their account for this reason, no? At that point, just cut out the middle-man and let people change their username.