As a user who needs to reach people about an imported task, or to access other information missing on phabricator, but who has no (complete) idea of the first ten years of history of the issue tracker, I want to be educated about the fact that additional information and tools to solve me issue may be available at old-bugzilla.
Concretely, a hover text or something around "Reference" should say something like "additional information about this task, including contact information of interested people, may be found in the referenced source".