I don't have access to them, but I would guess that the template is something like this:'Changed %s1 from "%s2" to "%s3"'The real template will depend on the language you're using ...
I see now. This is actually a virtual field which is templated when viewing an activity log/campaign results, not a database field, so we would not return it via the API. You could...
You can use "is" for external URLs, Marketo just has to have registered a visit to the page already in order for it to be considered a valid target for the trigger/filter.
Are you not using a Marketo landing page as your unsubscribe page? The noscript version of the form from a direct-embedded form should work just fine regardless of whatever script-...