A few earlier threads.
Not dead, but deleted accounts and obs and IDs unhappen
https://forum.inaturalist.org/t/the-vanishing-of-a-fellow-inatter/38221
https://forum.inaturalist.org/t/dealing-with-account-deletion/93
https://forum.inaturalist.org/t/handling-top-identifier-status-for-deceased-inatters/28384
And this
https://forum.inaturalist.org/t/deceased-observers-and-a-deceased-symbol-on-their-icon/642/68