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@Undo I've added it to the post, but don't think it's relevant - same bug happened today to somebody else on iPad. (this is what made me find this old report of mine :-))
According to this answer, the editor was previously not fetched for answers (not sure if this was the case at that time), and this answer says that previously any user that returned nil would be erroneously attributed to "Community". So I assume the post was incorrectly trying to attribute the editor and failing.
Both of those situations have now changed (editors are always shown with the new style attribution, and users can now return nil), so this is no longer an issue.