Ævar (http://en.wikipedia.org/wiki/User:Ævar_Arnfjörð_Bjarmason) made a tool recently that enables bureaucrats to rename users and told me yesterday that Tim Starling has just deployed it at the servers.
Therefore, any bureaucrat can change the username of users on their wiki using [[Special:Renameuser]].
For more details, please see http://en.wikipedia.org/wiki/Wikipedia:Changing_username http://meta.wikimedia.org/wiki/Changing_username http://meta.wikimedia.org/wiki/Requests_for_permissions#Requests_for_name_ch... http://meta.wikimedia.org/wiki/Stewards#Instructions_for_changing_usernames http://en.wikipedia.org/wiki/Wikipedia:Bureaucrats#Instructions_for_changing...
Please translate this into your language and let the people on your project know about this new process. People on wikis without bureaucrats can make their request at [[meta:Requests for permissions]] instead.
Angela.