Thank you, @Jonathan_DOI! It’s incredibly helpful to hear more about how you think of persistence. I had not seen Andrew Treloar’s 5 persistencies. It is a wonderful resource and something I’d like to share within our communities for discussion.
It’s also helpful to hear about the DOI edge cases. As an organization working with Crossref and DataCite to assign DOIs, we try very hard to keeps records/objects for which we’ve assigned DOIs available. But as you say, there are cases where an object should never have received a DOI. When a duplicate DOI has been assigned in error, we have been use the related identifier metadata fields to create a persistent link between the DOIs. Knowing which DOI to consider the “correct” DOI is another interesting question.