Jelly doco for Create Issue tag says that default value of reporter tag is the current logged in user. But it ain't that simple.

We need to document the subtleties of when you can go without specifying the reporter attribute of the CreateIssue tag, and when it becomes mandatory. It is related to the Modify Reporter privilege. See JRA-12984 for a description of the underlying issue.

I'll update the doco.

Cheers,
Ian