Nice article. Some observations:
1. I don't understand the difference between 'unique', 'owned' and 'isolated'. (Some other systems use 'isolated'.) Is there a difference?
2. I suspect that 'owned' does not need to be a type qualifier - it can be a storage class much like 'ref' is. This makes for a much simpler implementation.
3. Taking it a step further, I suspect that 'owned' can be implemented as a library type, ala owned!T, with only a smidgen of compiler help.
