Clarification
To me (a relatively new user) the current feature request / bug tracking system here on MSO seems to be rather chaotic and somewhat difficult to comprehend. Having had some time since originally posting this question, I think I've hammered down what I was intending to find out a bit more accurately now:
Lots of [feature-request]
tagged questions have never gained a [status-*]
tag (compare the total number of feature request questions to the number without any status tag, remembering to discount those that are closed) and there are some questions have obviously gained a lot of support (votes) and have any much discussion without ever gaining a status (check the top voted of those with no status tag for examples).
The available status tags look pretty comprehensive to me, as far as I can tell every request should match a status (even if it's "deferred" for "we're ignoring this until later"), but given there are many "open" feature requests how do we tell the difference between those without a status that might eventually happen (worth supporting) and those that are effectively declined (a waste of time supporting)? Is the "default" for a requests effectively the deferred tag? Or should those with no real moderator input be assumed to be declined?
And, assuming a feature request hasn't been declined or otherwise completed, how do I effectively add my support to help the request along?