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 <email@example.com>, Zendesk would set the user's name to "Priscila Zendeskian". However if the header just shows:
From: <firstname.lastname@example.org>, 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.