Using a custom “Can View” policy prevents being able to add a subscriber when mentioning them in a new comment with an @name, unless author or @name in question is an Administrator. For non-administrators the name appears greyed out. Author is able to add @name as a subscriber by selecting that as an action, but typing into a new comment doesn’t allow this.
Would expect @name referenced in a comment this way to automatically be added as a subscriber.
phabricator 67f062b0049dcc55558acfa85c6333947d6fcaab (Fri, May 31)
Set default Maniphest “Can View” Policy is as above (where acl*it-general contains a handful of individuals within the IT department)
Create a new Maniphest Task & Save
Add a new comment and @name somebody within it. That individual is not subscribed or notified.