I had thought that any question tagged
untagged was as a result of migration. But
What happened to the village in Contagion? was not migrated from anywhere as far as I can tell, so how did it end up untagged? Perhaps it was asked by someone with tag-creating rep, but after a long enough time with only one question, the tag went away? What are the various ways that a question can end up tagged as
Also, can a tag be added to such a question, or must
untagged be removed when another tag is added?