Karbon provides various collaboration functionality on emails, including commenting and the ability to add the email to a work or contact timeline. To ensure everyone can always perform these actions, colleagues BCC'd on an email will be visible to other team members.
Anyone who receives an email as a BCC recipient will be able to collaborate on that email like any regular recipient.
BCC recipients will only be visible within Karbon. Outside of Karbon, BCC'd recipients will always remain anonymous.