Starting with LEPTON 4.4.0
If you like to add additonal chars to the check of username, display name and email please check the lepton.ini.php inside the config folder and modify the values to your needs.
Standard values are (see class lepton_handle):
emails: a-zA-Z0-9@\-_\. usernames: a-zA-Z0-9@ \-_\.
Additional chars in lepton.ini.php are set for german umlauts as standard.
; Set allowed additional chars for email and usernames (extends LEPTON_handle methods) [custom_vars] additional_email_chars = ' ' additional_usernames_chars = 'äöüÄÖÜ'