What's the Comments icon that's next to some requirements?

When a requirement is selected in a structure, you can click the Comments link on Standard view to create a comment.

In the Comments dialog, type in your comment and click the Publish button. When a comment is published, the default status is Open. You can set the Change Status field to Closed, and back to Open. If the requirement has at least one Open comment, an icon displays next to the requirement in the structure, which alerts the product manager or requirement owner of actionable comments.