This older thread answers many questions: https://forum.inaturalist.org/t/dealing-with-account-deletion/93/1
This newer thread is still open and it’s probably best to concentrate discussion there if acceptable: https://forum.inaturalist.org/t/the-vanishing-of-a-fellow-inatter/38221
I’m happy to merge these posts into that one if @diegoalmendras has no objections.