The term "Opt-In" and "Opt-Out" should be avoided as they are unclear. They are unclear because they can be used to define a Process, State, or Default

Process: Where Opt-In is describing the act of a patient agreeing to participate. Where Opt-Out is describing a patient disagreeing to participate.

State: The state of participating, vs the state of not participating. Yet what is participating?

Default: Where Opt-In is defining that when there is no consent on file, that the patient is not participating - Explicit Consent. Where as Opt-Out is defining that when no consent on file, that patient is participating - Implicit Consent.

The following text at the beginning of Interpretation is an example of this lack of clarity.

"The Consent resource is structured with a base policy which is either opt-in or opt-out."

The base policy (Consent.policy) needs to point at a more exacting policy, not something so unclear. It is possible for HL7 to define some base policies, however I don't think we can include sufficient exacting detail that everyone globally will get the same results. For example base policies need to include inside of them specific rules about User Provisioning, Role-Based-Access-Control, acceptable use, punishment for unacceptable use, access to an accounting of disclosures, etc.