you shoudl review your use of firstname + lastname - some languages and sites will use different name fields, different orders etc, so Moodle provides the fullname() api that helps with this.
note - this is not a blocker for approval - feel free to close as won't fix.
https://github.com/praxisdigital/mod_diplomasafe/blob/MOODLE_311_STABLE/classes/diplomas/api/mapper.php#L78
you shoudl review your use of firstname + lastname - some languages and sites will use different name fields, different orders etc, so Moodle provides the fullname() api that helps with this.
note - this is not a blocker for approval - feel free to close as won't fix.