Sorry for taking an eternity to reply (again).
On the first point: Good point! I’ve now finally fixed the SSA probabilities so that they sum up to 1, which really they should, to really have a version of EDT.
>prevents coordination between agents making different observations.
Yeah, coordination between different observations is definitely not optimal in this case. But I don’t see an EDT way of doing it well. After all, there are cases where given one observation, you prefer one policy and given another observation you favor another policy. So I think you need the ex ante perspective to get consistent preferences over entire policies.
>(Oh, I ignored the splitting up of probabilities of trajectories into SSA probabilities and then adding them back up again, which may have some intuitive appeal but ends up being just a null operation. Does anyone see a significance to that part?)
The only significance is to get a version of EDT, which we would traditionally assume to have self-locating beliefs. From a purely mathematical point of view, I think it’s nonsense.