>The coalescing is two-level: first, simple duplicates are weeded out. Second, if the update queue gets very full, it becomes coarser-grained, and weeds out duplicates based on that coarser grain

This is not about duplicates. For example, sync updates 100 items in a list changing their titles. Items are bound to a list in the UI. Thus, 100 unique title update events triggered.

>Events are only used in the M→V communication

I don’t understand. Button clicked -> model change -> view update -> new event triggered -> model or view updated again … This is not something one would code on purpose, but often an attempt to create relationships between view. Like a custom layout code. Might not include model at all, just views being updated in an event handler trigger more events and more updates to views.