This is very detailed, way more interesting facts than I was expecting.
I think many of the sections cover big enough topics that they could've been whole posts, so probably not an introduction level post. But personally I liked that, good to see some in-depth posts!
A RefCell is not threadsafe
Just to clarify for those less familiar with Rust: you can't actually do anything unsafe - you just can't share it between threads at all, it won't compile.
I tend to end up with RwLocks when doing threading code, not sure if that's a problem... Probably not super performance, but it's easy, and I like the way Rust ensures that you lock long enough but not too long.
I only found out after a while that RwLock exists and while less fair, is often faster than Mutex (which seems to be the most mentioned online). [By 'less fair' I mean that, in my understanding, it does not give equal chance to each thread... I think it can starves out writes?]