how to set custom author while adding comment

[Nic Brough -Adaptavist- · Accepted solution]

You don't.   The point of a tracker is that it tracks who entered a comment.  If an agent is doing it, then it's based on a call or email from a client (who should be encouraged to use the portal) and they should say that in the comment.

[RAHUL DESHMUKH]

The problem is ,I need to pass my application's username to JIRA while adding a comment

[Nic Brough -Adaptavist-]

Same point - it's logging the agent who actually makes the comment because that's what it's for.