The username does not appear in the comments on Instagram.

When tested on two accounts One is that the username appears normally One does not show a username.

When you debug both tokens, the permissions are found to have been acquired equally.

Why does this happen?

account access_token debug - permissions

email, read_insights, pages_show_list, business_management, pages_messaging, instagram_basic, instagram_manage_comments, instagram_manage_insights, instagram_manage_messages, pages_read_engagement, pages_read_user_content, public_profile

pages_show_list - Applies to all objects
business_management - Applies to all objects
pages_messaging - Applies to all objects
instagram_basic - Applies to all objects
instagram_manage_comments - Applies to all objects
instagram_manage_insights - Applies to all objects
instagram_manage_messages - Applies to all objects
pages_read_engagement - Applies to all objects
pages_read_user_content - Applies to all objects

Query used

178****************6/comments?fields=hidden,id,like_count,media{id,shortcode},replies{text,media,timestamp,username,user,id,like_count,hidden,parent_id},text,timestamp,username,parent_id,user,from&limit=5

When operating normally

    {
      "hidden": false,
      "id": "1805**********3",
      "like_count": 0,
      "media": {
        "id": "184******26",
        "shortcode": "C_******Q"
      },
      "text": "***********",
      "timestamp": "2024-09-03T14:18:09+0000",
      "username": "k*****i",
      "from": {
        "id": "90697*********133",
        "username": "k********i"
      }
    },

If an error has occurred

    {
      "hidden": false,
      "id": "18***********03",
      "like_count": 0,
      "media": {
        "id": "178510*********46",
        "shortcode": "C******c-"
      },
      "text": "**************",
      "timestamp": "2024-09-06T06:13:53+0000"
    },