You may sign in using any WikiWord as a user id. (Any characters in ÀñíçéàÖãæôßøü etc. may be used too). The user id will be used as a link in RecentChanges to your home page.
Note: Only if you create your personal HomePage with same the pagename as your user id, you will be able to store your UserPreferences. Otherwise not.
New users may use an empty password.