Answers
Do Not Contact, and what we refuse to pretend
Open any contact record and, once it is set up, a Do Not Contact button sits on it. What it does depends on which CRM the contact lives in, and we tell you which, every time, instead of letting one word mean two things.
In Keap: your tag, your automation
Pick the tag that means do not contact in Settings → Tracking. The picker lists every tag in your Keap and narrows as you type, because scrolling a bare dropdown of three hundred tags is nobody's idea of software. The button applies exactly that tag, so whatever automation you already wired to it runs the way it always has. We never create the tag for you, and we never touch the email opt-in state: Keap's API has no working way to set it, and anything claiming otherwise would be a promise nothing kept.
In HighLevel: the real thing
HighLevel carries do not contact as a field on the contact, so the button sets it directly and HighLevel genuinely stops contacting them. No tag to choose, nothing to configure.
When a person lives in both
Both get written, and if one side fails we say which one landed and which did not, because a person you believe is suppressed everywhere and is not is the worst kind of wrong. Every use is also written as a note on the contact, which is the record that outlives ours.
The double confirmation is not decoration
The second confirmation names the person and describes the actual mechanism for their CRM, tag or field, so it cannot be cleared by reflex. The server asks for confirmation as well; a safeguard that lives only in a browser is a dialog, not a safeguard.