Sad news. I had the honor of participating in a workshop he organized on Inconsistency Robustness in 2011, that was an interesting gathering.

https://www.amazon.com/Inconsistency-Robustness-Studies-Logi...

Probably, the most fundamental misunderstanding of the Actor Model is that it is based on "Event Loops" which require the following: When an Actor receives a message, it must run until it produces a response to the message and then loops back to receive another message. However, a ReadersWriter scheduler must be able to receive more read and write messages even while it is still processing a message as explained in https://www.amazon.com/Inconsistency-Robustness-Studies-Logi... Even so, a ReadersWriter scheduler must obey the Mutual Exclusion Principle, which says that only one activity can execute in an Actor at a time.

Another common misunderstanding is that an an Actor must have a mailbox, message queue, or event queue. There would be an infinite regress if any of these were required because since everything is an Actor, each of these would itself need a mailbox, message queue, or event queue!