When clicking on media gallery posts in the Activity Story Stream widget triggering the file preview in the modal and then using the "next" and "previous" arrows to navigate through the other posts within that gallery, if you try to add a comment on a post that was not the one you had originally opened your comment will not be added to that post. The comment does get added, but it gets added to the post that had been originally opened in the modal.
We are using: 7.1.1.30142