Gabriel,
I'm not sure about the implications this might end up causing, but an option in Portal-ext.properties file might help?
# By Default liferay will not allow mutlibyte characters and non-english characters like �
# set the below flag bypass.liferay.screenname.validation to true
# to make liferay to allow those characters
bypass.liferay.screenname.validation=false
flip the above to true and restart USS and test?
_R