Collaborators not appearing in Collaborators List

On notes shared by another user with me, the Collaborators List on my end does not list that user as a Collaborator, therefore appearing as what one would think to be a note shared with no one that came out of nowhere. Notwithstanding, the note does sync on both ends when either user edits it.

This can lead to actions that would cause **note duplication and potential data loss.**

This issue is shared with the web, macOS and iOS versions (see more detailed description in the [reported issue](https://github.com/Automattic/simplenote-ios/issues/272) in the latter repo)

Start by reading the linked Simplenote iOS issue 272 for the detailed reproduction and compare the Collaborators List behavior across the web, macOS, and iOS versions. Trace how a note shared by another user is represented locally; done means the other user appears as a collaborator and editing the note cannot lead to apparent duplication or data loss.

Written by the indexing model from the issue text.