I am having the same issue as this post (locked). https://www.easy-profile.com/support/new-user-activation-email-contains-formatname-as-username.html
The email subject states: Account Details for formatName at...
Body contains: Hello formatName, Thank you for registering at...
I am pretty sure that it boils down to the language file COM_USERS_EMAIL_REGISTERED_BODY_NOPW but am not sure where to go from there, since deleting %s causes the subject to show as "COM_USERS_EMAIL_ACCOUNT_DETAILS"