Suppose you have someone who did a bunch of writing in America, then moved to Europe and became famous as an inventor there. Under your proposal, this person has both Location:Europe and Location:USA, and both Occupation:Writer and Occupation:Inventor. They therefore show up for queries for European writers and American inventors, neither of which was intended; I bet we can come up with situations where the false positives are even worse. The presence of those tags have to be interpreted in light of each other.

If you do this naively I think it's pretty clear you've either sacrificed expressivity or made the system a LOT more complicated/harder to understand. At best you end up with some kind of product structure in (what is no longer just) the set of tags on an article. You can think of explicating an implicit product structure in joining "American" and "Writer" in the same object. But I think if you've started talking about compound tags, you're really talking about something other than a tagging system.

I think the only feature you need to express this is to be able limit a tag to the context of another tag. It's slightly different than a compound tag because each tag can still be used independently.

I experimented with a system like this recently[0] that used two different tag notations that seemed to make the mixing more intuitive. I didn't have enough time to iterate on it further or build it more seriously, but I think there is potential in this area.

[0] https://youtu.be/bi3YkY7UKmM

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To be more specific, your entity could be tagged as Location:Europe in the context of Occupation:Inventor, and Location:USA in the context of Occupation:Writer. I still think the entity should match queries for any of the 4 tags, it just shouldn't match a query {Occupation:Inventor/Location:USA}

That introduces a dependency, or at least ordering, between the concepts of Location and Occupation that I'm not sure should exist, much less which direction it should point. It works for baking:skilled because skill level is inherently part of the property of being a baker, and skill is undefined without a thing to be skilled at, whereas someone can easily reside in a location with no occupation ({Location:USA/Occupation:Layabout}?) or have an occupation with unknown/unfixed location ({Occupation:Inventor/Location:Nomad}?).

And if you try to create a synthetic context to place both tags under, you get... compound tags, or close enough as makes no difference to me. :) I'd 1000x rather start from there, and special case it to return results for each tag individually, than start introducing spurious orderings or dependencies. (ed: maybe it would be clearer to say "composite tags", as in tags composed out of other tags?)

Perhaps I misunderstood the example but I thought the point was precisely that there is a dependency between Occupation and Location which individual tags cannot express...?