Comment parents sometimes appear twice in a content-comment activity

Here is sample JSON, it is the content-comment activity:

```json
{
  "items": [
   ...,
    {
      "oae:activityType": "content-comment",
      "oae:activityId": "1372183887315:TTh9DoCfcNJ",
      "verb": "post",
      "published": 1372183887315,
      "actor": {
        "oae:collection": [
          {
            "oae:id": "u:oae:TTOF24QRN5",
            "oae:thumbnail": {
              "url": "/api/download/signed?uri=remote:https://si0.twimg.com/profile_images/1210335187/hoofd_normal.jpg&signature=753fe6aef8ffcfbf9c78b5e331779b329c0310f4&expires=1372248000000",
              "width": 32,
              "height": 32
            },
            "oae:visibility": "public",
            "oae:profilePath": "/user/oae/TTOF24QRN5",
            "displayName": "Simon Gaeremynck",
            "url": "http://oae.oae-qa0.oaeproject.org/user/u:oae:TTOF24QRN5",
            "image": {
              "url": "/api/download/signed?uri=remote:https://si0.twimg.com/profile_images/1210335187/hoofd_normal.jpg&signature=753fe6aef8ffcfbf9c78b5e331779b329c0310f4&expires=1372248000000",
              "width": 162,
              "height": 162
            },
            "objectType": "user",
            "id": "http://oae.oae-qa0.oaeproject.org/api/user/u:oae:TTOF24QRN5",
            "oae:tenant": {
              "alias": "oae",
              "displayName": "Open Academic Environment"
            }
          },
          {
            "oae:id": "u:oae:PVu1ZDIxNM",
            "oae:thumbnail": {
              "url": "/api/download/signed?uri=local:u/oae/PV/u1/ZD/Ix/PVu1ZDIxNM/profilepictures/small&signature=ee04e3c12469eb69df2adad2c3b254009096295a&expires=1372248000000",
              "width": 32,
              "height": 32
            },
            "oae:visibility": "public",
            "oae:profilePath": "/user/oae/PVu1ZDIxNM",
            "displayName": "Uma Bhupathiraju",
            "url": "http://oae.oae-qa0.oaeproject.org/user/u:oae:PVu1ZDIxNM",
            "image": {
              "url": "/api/download/signed?uri=local:u/oae/PV/u1/ZD/Ix/PVu1ZDIxNM/profilepictures/medium&signature=3c401fd9958d8d9eeb0061eb20c533b68aa55a87&expires=1372248000000",
              "width": 162,
              "height": 162
            },
            "objectType": "user",
            "id": "http://oae.oae-qa0.oaeproject.org/api/user/u:oae:PVu1ZDIxNM",
            "oae:tenant": {
              "alias": "oae",
              "displayName": "Open Academic Environment"
            }
          }
        ],
        "objectType": "collection"
      },
      "object": {
        "oae:collection": [
          {
            "oae:id": "c:oae:VeN4GJMk0f#1372183181638",
            "oae:messageBoxId": "c:oae:VeN4GJMk0f",
            "oae:threadKey": "1372183181638|",
            "url": "/content/oae/VeN4GJMk0f",
            "content": "Y U NO MAKE ME MANAGER?!",
            "author": {
              "oae:id": "u:oae:TTOF24QRN5",
              "oae:thumbnail": {
                "url": "/api/download/signed?uri=remote:https://si0.twimg.com/profile_images/1210335187/hoofd_normal.jpg&signature=753fe6aef8ffcfbf9c78b5e331779b329c0310f4&expires=1372248000000",
                "width": 32,
                "height": 32
              },
              "oae:visibility": "public",
              "oae:profilePath": "/user/oae/TTOF24QRN5",
              "displayName": "Simon Gaeremynck",
              "url": "http://oae.oae-qa0.oaeproject.org/user/u:oae:TTOF24QRN5",
              "image": {
                "url": "/api/download/signed?uri=remote:https://si0.twimg.com/profile_images/1210335187/hoofd_normal.jpg&signature=753fe6aef8ffcfbf9c78b5e331779b329c0310f4&expires=1372248000000",
                "width": 162,
                "height": 162
              },
              "objectType": "user",
              "id": "http://oae.oae-qa0.oaeproject.org/api/user/u:oae:TTOF24QRN5"
            },
            "published": "1372183181638",
            "objectType": "comment",
            "id": "http://oae.oae-qa0.oaeproject.org/api/content/c:oae:VeN4GJMk0f/messages/1372183181638",
            "oae:tenant": {
              "alias": "oae",
              "displayName": "Open Academic Environment"
            }
          },
          {
            "oae:id": "c:oae:VeN4GJMk0f#1372183887311",
            "oae:messageBoxId": "c:oae:VeN4GJMk0f",
            "oae:threadKey": "1372183181638#1372183887311|",
            "url": "/content/oae/VeN4GJMk0f",
            "content": "hmm",
            "author": {
              "oae:id": "u:oae:PVu1ZDIxNM",
              "oae:thumbnail": {
                "url": "/api/download/signed?uri=local:u/oae/PV/u1/ZD/Ix/PVu1ZDIxNM/profilepictures/small&signature=ee04e3c12469eb69df2adad2c3b254009096295a&expires=1372248000000",
                "width": 32,
                "height": 32
              },
              "oae:visibility": "public",
              "oae:profilePath": "/user/oae/PVu1ZDIxNM",
              "displayName": "Uma Bhupathiraju",
              "url": "http://oae.oae-qa0.oaeproject.org/user/u:oae:PVu1ZDIxNM",
              "image": {
                "url": "/api/download/signed?uri=local:u/oae/PV/u1/ZD/Ix/PVu1ZDIxNM/profilepictures/medium&signature=3c401fd9958d8d9eeb0061eb20c533b68aa55a87&expires=1372248000000",
                "width": 162,
                "height": 162
              },
              "objectType": "user",
              "id": "http://oae.oae-qa0.oaeproject.org/api/user/u:oae:PVu1ZDIxNM"
            },
            "published": "1372183887311",
            "objectType": "comment",
            "id": "http://oae.oae-qa0.oaeproject.org/api/content/c:oae:VeN4GJMk0f/messages/1372183887311",
            "inReplyTo": {
              "oae:id": "c:oae:VeN4GJMk0f#1372183181638",
              "oae:messageBoxId": "c:oae:VeN4GJMk0f",
              "oae:threadKey": "1372183181638|",
              "url": "/content/oae/VeN4GJMk0f",
              "content": "Y U NO MAKE ME MANAGER?!",
              "author": {
                "oae:id": "u:oae:TTOF24QRN5",
                "oae:thumbnail": {
                  "url": "/api/download/signed?uri=remote:https://si0.twimg.com/profile_images/1210335187/hoofd_normal.jpg&signature=753fe6aef8ffcfbf9c78b5e331779b329c0310f4&expires=1372248000000",
                  "width": 32,
                  "height": 32
                },
                "oae:visibility": "public",
                "oae:profilePath": "/user/oae/TTOF24QRN5",
                "displayName": "Simon Gaeremynck",
                "url": "http://oae.oae-qa0.oaeproject.org/user/u:oae:TTOF24QRN5",
                "image": {
                  "url": "/api/download/signed?uri=remote:https://si0.twimg.com/profile_images/1210335187/hoofd_normal.jpg&signature=753fe6aef8ffcfbf9c78b5e331779b329c0310f4&expires=1372248000000",
                  "width": 162,
                  "height": 162
                },
                "objectType": "user",
                "id": "http://oae.oae-qa0.oaeproject.org/api/user/u:oae:TTOF24QRN5"
              },
              "published": "1372183181638",
              "objectType": "comment",
              "id": "http://oae.oae-qa0.oaeproject.org/api/content/c:oae:VeN4GJMk0f/messages/1372183181638"
            },
            "oae:tenant": {
              "alias": "oae",
              "displayName": "Open Academic Environment"
            }
          }
        ],
        "objectType": "collection"
      },
      "target": {
        "oae:id": "c:oae:VeN4GJMk0f",
        "oae:visibility": "public",
        "oae:profilePath": "/content/oae/VeN4GJMk0f",
        "oae:resourceSubType": "collabdoc",
        "oae:revisionId": "rev:oae:eeMBs55c2J",
        "oae:wideImage": {
          "url": "/api/download/signed?uri=local:c/oae/Ve/N4/GJ/Mk/VeN4GJMk0f/previews/rev:oae:eeMBs55c2J/wide.png&signature=25f096b8de396b1f7a74bbdb6a8e2a281e034e60&expires=1372185900000",
          "width": 1070,
          "height": 500
        },
        "displayName": "This is an awesome document",
        "url": "http://oae.oae-qa0.oaeproject.org/content/oae/VeN4GJMk0f",
        "image": {
          "url": "/api/download/signed?uri=local:c/oae/Ve/N4/GJ/Mk/VeN4GJMk0f/previews/rev:oae:eeMBs55c2J/thumbnail.png&signature=b2f344a0df8278275462a82a85b67971f86efb8b&expires=1372185900000",
          "width": 324,
          "height": 324
        },
        "objectType": "content",
        "id": "http://oae.oae-qa0.oaeproject.org/api/content/c:oae:VeN4GJMk0f",
        "oae:tenant": {
          "alias": "oae",
          "displayName": "Open Academic Environment"
        }
      }
    },
   ...
  ]
}
```

The activity:

![image](https://f.cloud.github.com/assets/102265/704632/2e042bac-ddc5-11e2-8279-edc35440db2c.png)

The content item:

![image](https://f.cloud.github.com/assets/102265/704639/461cce56-ddc5-11e2-8349-c7de13d12ebc.png)