Yes I'm especially interested in what OP thinks about the overlap (or not?) between the ideas in this post and the ideas in this part of boats' post:

> One could imagine an alternative design in which instead of places being unpinned by default and opting into pinning, places are pinned (or perhaps “immovable”) by default, and have to opt into supporting the ability to move out of them. This would make it so that by default places have the least power (can only access via shared reference) and they gain a monotonically increasing set of powers (can assign to them, can move out of them).

> In addition to places having to opt into moving, there would be three reference types instead of two: immutable, mutable, and movable references.