comments: collapsed UI fix

* Fixes issue with collapsed comments overlapping in UI, see screenshots below:

Before:
![comments-before](https://f.cloud.github.com/assets/480478/1561207/41470414-502a-11e3-98a8-4f164393895e.png)

After:
![comments-after](https://f.cloud.github.com/assets/480478/1561208/4dc0b956-502a-11e3-93e2-2d7631389c10.png)

Signed-off-by: Adrian-Tudor Panescu <adrian.tudor.panescu@cern.ch>