Yes, affiliates are the only ones that can customize and update their referral code. They can do this by doing the following:
Go to 'Assets' > Click on 'Advanced' > Click on the 'Edit' icon.
Be aware that when a referral code has been updated, the previously created & shared referral codes will no longer work.
The referral codes are not case-insensitive, meaning that ?ref=JohnDoe and ?ref=johndoe are considered the same code.
If you want to disable referral codes you can go to your advanced program settings and disable Referral codes.
Note: If you don't see the little 'edit' pencil icon, it means that either your case does not support this kind of customization, or it means that you are using an older version of the code, and you might need to update your integration. Please contact our support chat to assess your case.