Comment by ralfj

> multiple immutable shared references are a form of contraction

No, they are not. You're not using a value more than once, you are borrowing it, which is an extension of affine logic but keeps true to the core principles of affinity. I have modeled multiple shared references in an affine logic (look up RustBelt), i.e. in a logic that doesn't have contraction, so we have very hard evidence for this claim.