I’ve always thought Pin was difficult to understand because it’s not explained in a clear way in the official docs. In particular, lots of documentation claims things like “Pin ensures that an object is never moved”, which isn’t true!

It’s only true if the object is not Unpin, but most normal objects are Unpin, so Pin usually does nothing. It took me a very long time to finally understand this. The set of types T for which Pin<T> does anything at all is very niche and weird and IMO this isn’t sufficiently highlighted by the documentation.