I have non-English characters in my name under my *.drupal.org profiles. However, at DrupalCon Denver 2012, these non-English characters couldn't get printed out on the badge; and it displayed "squares". Since DrupalCon is an international event, I believe I wasn't alone.
I suggest that for the future DrupalCon, if the printer won't be able to print out non-English characters, then DA sends an email to notify these attendees and give them option to update their registration using English-only characters.
Below is an email template from Google I/O:
We’re looking forward to seeing you at ****** this year, but noticed that your ****** registration was completed with non-English characters. Our badge printers are only able to print using English characters and we need all attendees to have badges. Your badge will show your first and last name, company name and claim to fame (if provided).
We apologize for the formalities, but getting this information from you now lets us make sure you have a smooth check-in experience when you arrive at the conference. If you don’t update your registration details ahead of time, you may need to wait in line at our registration help desk at the conference to fix this before your badge will be able to be printed.
Please update your registration information by MMMM DD, YYYY.
How to complete registration
Make sure you have a ****** account as it is required to register.
Visit the registration page
Complete your registration details. to get your confirmation number and you’re done!
If you have any questions or need help, please see our FAQ or email ******@****.***