What about long arrays? Is there a mechanism where Svelte knows which element is mutated, and do fine-grained recomputation/update only the corresponding view elements?

This is the primary place where we have to go outside the framework in React. Only a large linear list has this problem -- if it was a decently balanced component tree, then we could skip updating huge swathes of it by skipping at a top level node. But it is not possible in an array. You have it iterate through each element and do a shallow comparison to see if the references have changed.

That said, it is fairly easy to escape to DOM from inside a React component with useRef and the portal pattern. Then we can write vanilla JS which makes updates to only the values it changes.

If Svelte solves this in an elegant manner, then it would be a very compelling feature over React. I'm asking here because last I checked, most of the examples in Svelte's documentation pointed to simple counters and regular objects, and I couldn't find an example of a large linear list.