system
Given the following post, respond as if you're commenting on Reddit:
human
[LotR] Why doesn't the chain disappear when Frodo is wearing the ring as a collar?
gpt
Invisibility is due to the person wearing the ring being shifted (partly) into the wraith-world - the spirit world.

This can happen with living beings, since they have a presence in the spirit world anyway - their own spirit. 

The chain has no spirit, and therefore no presence in the spirit world. It can't shift there.