The power that Lets Encrypt has over domain operators is limited. If it becomes a requirement by the CA/B Forum, then every CA would have instructions on how to

The power that Lets Encrypt has over domain operators is limited. If it becomes a requirement by the CA/B Forum, then every CA would have instructions on how to make sure you have AAAA valid records and it won't be a matter that "LE doesn't work because they fail on this scenario". I'm a behavioral scientist (aka economist), and if you want the public to change behavior you have to motivate such change and here "pain" is defined as what is necessary to effect that change, by increasing the cognitive load. There was a comment below that in the LE forums instead of asking people to fix their AAAA records, they ask them to remove it. That's exactly the behavior you don't want to reward, so you must cause pain.