How is the requester's profile name defined when a ticket is created from a new user via email?
It depends on how the email is sent by the user's email account.
if the header in the source shows:
From: Priscila Zendeskian <firstname.lastname@example.org>
Zendesk would set the user's name to "Priscila Zendeskian"
However if the header just shows:
Zendesk would set as just the email prefix, "priscilazen".
See view the original email for more information on how to view the source header information in a ticket.