Thanks for sharing that context, James! 
So to sum up, it appears that at the moment we have five ways to indicate when a topic has taken its course and needs to be wrapped up. Does this about capture it?
| what | where | who |
|---|---|---|
 Discourse Solved |
Support Installation Dev Data & reporting SSO | topic owner, @team, TL4 |
| fixed | Bug UX (works everywhere) | @team |
| completed | Feature UX | @team |
| delivered | Marketplace | all members |
 close topic |
everywhere | @team and automatic |
This does feel to me like an awful lot of variety. I don’t know why the tags are different. Maybe it is helpful/informative for folks to be able to scroll through those tag lists individually. These tags and their purpose are not so discoverable, however.
solved is easily discoverable and works quite well for support. I think it makes sense to limit it to that category. It’s helful to be able to filter for solved/unsolved topics in that category - I often forget about that pulldown though and wishit were more discoverable in the UI. 
fixed is only used in Bug UX and means a bug or UX bug was fixed.
completed is used in Support Feature UX as well. UX because UX topics are often also feature requests. There was one topic, "Reader Mode" theme component feedback, that was in Site feedback but I’ve now moved it to Theme component where it seems to belong now that the component has been released.
delivered is only used in Marketplace.
Topics are closed for a variety of different reasons:
- Support topics are closed a month after the last reply, once solved
- Marketplace topics are closed a month after the last reply, whether or not they are delivered.
- moderators close topics
- when they are resolved
- to prevent replies (eg documentation or release-notes)
- as moderation tactic to end discussion in topics that have become unproductive or have run their course
Some potential next steps:
- add descriptions to fixed completed delivered tags that explain how we use them
- create a data explorer query with results like the table above, but listing the real and up to date number of topics that are solved/ unsolved, fixed/not fixed, completed/not completed, delivered/not delivered
- create a data explorer query that lists the topics that have been closed, fixed, completed, delivered in a given timeframe
- create a topic here in Site feedback to share the results of the above queries each week using an automation
- create a topic here with a little howto guide for wrapping up topics and get a team together to follow it to start working through the list, in reverse chronological order