JIRA Service Desk introduced several restrictions on what Collaborators can do on a project. So when such user is triggering post-functions from linked issues in regular projects where they have elevated privileges, usually they fail because of those restrictions. Typical scenario is a Service Desk Project (1st tier) with a Engineering Project (2nd Tier). Users in Engineering typically are given the Collaborator role in SD.
It would be nice to have the ability to specify a "Run As" user for those post-functions affecting issues where the executing user has limited privileges. This is how JSD automation also works.
Post-functions that should support this feature:
8 - Copy Field Value to Linked Issues Function
10 - Set Field Value Of Linked Issues Function
16 - Transition Linked Issues
18 - Comment Linked Issues (I'm not sure if this is required, Collaborators already have the permission to comment).