Can I lock an issue so the Reporter or Assignee are the only users that can action the issue

[Cameron]

Is it possible to set security that the Reporter and Assignee are the only users that can action an issue through the workflow? If possible it would be great to also leave the comments open to any other user that has view ability.

[Nic Brough -Adaptavist- · Accepted solution]

"Action" is a noun, not a verb.  You can't "action" something, it's corporate meaningless nonsense.

Your desired flow is clear though, and Jira supports it because it is a very useful thing to do.  Have a look at "conditions" in the wokflow  - these allow you to say things like "only reporter and current assignee can do this"