For a while now, I've noticed the appearance of tags in the comments toolbar that you can't use or have no purpose. I know from recent experience that when you link to a YouTube video when you post a comment, the video appears. This is not the case for images but seeing how Digital Photography School has enabled that feature (see my comment in the following link) made me ask this question here.
It's not only cool but also increases the comment appeal by being able to link to an image to support their discussion.