The tag for disagreement is good because it flags the information for the reader to pay extra special attention and to think about what they are reading more carefully. Futher more he thinks that it could encourage people to contribute to the issue by editing content (or placement of content.) The potential is to be an active reader rather than passive on and spur on interactivity.
I also like the opposite idea, that it is a good thing that some pages don’t have the banner, because that shows agreed upon information or no known disagreements.
Can you imagine these examples: