> In Rust it's the overt explicitness of the borrow checker, and the friction it adds to one's programming.

Most, and perhaps all of the "friction" that the borrow checker adds to exploratory programming can be fixed with comparative ease by adding a few well-placed `.clone()` calls (for immutable data) and/or changing some type declarations to `Rc<RefCell<…>>` - at a minor cost to performance, in both cases. One might think that Rust needs to do more to support this use case, but given the performance implications, this is one example of how explicit can be far better than implicit. Regardless, it's absolutely the case that you can write "ALGOL" in Rust, just as you can write FORTRAN in any language. The code might not be at peak performance, it might even leak memory in rare cases, but it will do what you expect it to do otherwise.