A post that has earned the "sources needed" annotation usually (in my experience) has several comments explaining what the problems in the post are. These comments are still relevant (until the author addresses them), so they shouldn't be flushed or hidden. But they push the annotation down on the page where it can be more easily missed. Annotations are supposed to be rare; when they are used at all, therefore, they should be clear to all readers so the problems can be addressed one way or the other. Right now, though, they can get kind of lost on the page.
Shouldn't an annotation, being an intentional moderator action, have some priority placement? Can we improve on this?