Well FWIW, the original poster's anti-C++ statements aside, removing the borrow checker does nothing except allow you to write thread-unsafe (or race condition-unsafe) code. Therefore, the only change this really makes is allowing you to write slightly more ergonomic code that could well break somewhere at some point in time unexpectedly.
Nope. Anything which wouldn't pass the borrowck is actually nonsense. This fantasy that magically it will just lose thread safety or have race conditions is just that, a fantasy.
The optimiser knows that Rust's mutable references have no aliases, so it needn't safeguard mutation, but without borrow checking this optimisation is incorrect and arbitrary undefined behaviour results.
