Similar to the permission granting visibility into an incident when a user is mentioned in the ticket.... If a task is assigned to a an agent user or task user, that should allow them visibility into the entire ticket to view all the details of the incident/service catalog item, giving them visibility into correspondence between the requester/all comments.
Scenario - For a new hire service request/catalog item, there are various tasks that go to teams (based on the selections when filling out the catalog item). Instead of giving all agents or task users the permission to view all new hire tickets... grant a permission to read/manage an incident when they have a task assigned.