See PHI1905. An install with data retention requirements would like better support for avoiding ephemeral / external references, e.g. a user linking to an external chat service in a comment ("See more info here...") when there may be a retention policy mismatch between Phabricator and the service. Later, this may make it difficult to satisfy an auditor or regulatory requirement because the information has evaporated.
As a first step, letting Herald identify these links in comments seems helpful. Previously, see T13283. This is now straightforward.