There is a level of oversimplification beyond which the solution stops serving its purpose.

If this discussion board was just a shared doc in which everyone could write, that might be a "too simple" solution. Basic control over one's writing is what we expect in solutions such as this.

With Milk Kanban, it might have been just asking people to tell Kasia when they take the last carton. Would it be a simpler solution? Yes. Would it work? Well, I guess there is a reason why we do have these index cards.