Official answer received from "Eventbrite Customer Support" as follow (request id: 619986):
Thanks for reaching out!
For emailing attendees via our official "Emails to Attendees" feature, there is no way to personalize it to each attendee without sending individual emails and calling out the specific attendee. If you are sending a bulk email to multiple attendees there won't be a way to include any personal messaging to individual attendees.
I hope this info helps, and please don't hesitate to reach out if you have any additional questions! If you have any developer-specific questions you may want to reach out to our developer team at api@eventbrite.com.