While I wasn’t able to disable the requirement for the optout link, I am hiding it in white tiny font at the bottom of the invitation message. We needed to do this for external messages as well since we are using a custom subscription center survey  instead of the generic optout..

Thanks ​@InessaG 

I’m actually doing something pretty similar at the moment, so hopefully this will help you out too: By editing the OptOut tag to  ${l://OptOutLink?d=} it’ll place an anchor tag with no label (example <a href=”https://qualtrics.com”></a>) so the link will exist in code, but there’s no text associated with it, making it totally invisible.

The reason for my question here is, some of my more technical users have figured out how to extract the opt-out link, and the documentation suggests it’s only mandatory if you’re surveying outside your organisation.