More thoughts: I think of categories as contexts. My basic test for “should this be a different category?” is: would this have different access permissions[1], tag rules, or topic workflow? If not, probably not a different category.
Tags are associated with categories via tag groups — not necessarily 1:1. (However, if a tag has a different meaning in a different context, it should be a different tag.[2])
The sidebar menu, as well as existing notification configuration, shows tags separate from this context. That is potentially confusing to users.
“very different set of moderators” falls under this ↩︎
This runs into a problem when there are synonyms — but usually there’s a way around that. It might be nice to be able to consider tags with the same name in different groups to be actually different, possibly with tag group icons to help disambiguate… ↩︎