Zoho Project API - Comment post behalf of user from admin account

Zoho Project API - Comment post behalf of user from admin account

Hello, 

We're trying to integrate slack bot with Zoho API's. We wanted to make a feature where some one post there reply in slack then that reply comes and posted in particular task from that user. To achieve that add comment API should accepts user id or added by details. But right now its not accepting it. Can anyone help on this.