Part of your confusion seems to stem from the idea that IDs are something you can register like an ENS/DNS name, wherein different people could end up with a string attributed to them. ION specifically removes this whole class of issues due to its self-certifying inception event for creation of IDs, and it's non-transferability properties.
Discussion
To own or take someone's ID string, you'd literally need to take control of their current recovery private keys, you can't Sybil your way to that.