I have been able to get the comments to appear as posted by the correct user (impersonate?) on Jira from DevOps.

In the other direction (Jira>DevOps) they only show on DevOps as being posted from the Exalate user. 

I've tried:

workItem.comments     = commentHelper.mergeComments(workItem, replica)

And also tried:

issue.comments = commentHelper.mergeComments(issue, replica){ it.executor = nodeHelper.getUserByEmail(it.author?.email) }

Also tried:

{ it.executor = nodeHelper.getUserByEmail(it.updateAuthor?.email) }

Anyone able to advise?

Thanks