Shipment comment

I am trying to update a comment for an existing shipment, but I keep getting err mssg:

{"message": "Could not save the shipment comment."}

API and example I’m using are :

Method:POST

Request: {{base_url}}/rest/all/V1/shipment/1/comments

{
    "entity": {

      "parent_id": 0,

      "comment": "test_test",

      "is_visible_on_front": 1

    }
}

Is it even possible to update comment for shipment ?

Thanks in advance.