> Which means sites that have responsible moderation can still allow anonymous contributions.

Anonymous contributions, up to the point of somebody compromising the service? With the quantity of password hash thefts, I suspect we'll see even more ID thefts this way.

I can't imagine using any service that asks for ID, except perhaps from the well-established giants, so an exception for identifiability would effectively be a gigantic moat granted to the largest internet companies to keep out competition. Anything like that would need to be paired with massive anti-trust changes, as well as perhaps government take-over of the giants as utilities, none of which sounds very appealing...

That said, don't take any of my rambling as discouragement, your type of thinking is exactly what we need, we need massive amounts of policy discussion and your suggestion is very innovative.