Looks like I should have, to quote my father, looked with my eyes and not with my mouth... or in this case, keyboard.

Solution found here:

support.microsoft.com/default.aspx

The problem probably is that the portal  listings are being stored at the
home level, and customized permissions for a particular area  won't allow
a user to make edits to lists at the home level. So you would have to
give them rights  to Home.

Go into Manage Content for your sub area and for Home and see which area
is actually storing the portal listings.

If you want users to manage  listings you must give them "Manage Area"
rights. listings  do not live in lists but rather within a separate
table of area-level information.

Most of these listings  are a result of the Add listing  pre-checked checkbox when uploading a document  in to a document libarary. Is there an "approved" method to uncheck the checkbox by default? If not, can these listings automatically be expired / deleted from the Portal Listings?

I've found this article covering two methods of customization, but worry about long term effects on both performance and possible MS Support. blogs.msdn.com/.../355342.aspx

The link you referenced is the only work around I have seen for removing the auto portal  listings. You can backup the original file before you made the edit  and store it in a safe location (that gets backed up). That way if you do run into a situation where you have placed a product support call and they get to that page and claim they can’t help you because you are unsupported, you can roll back the original version and return to “supported status”.

I know of no list in SharePoint that will expire items  for you. Everything from what I have experienced has to be manually deleted unless perhaps you figure something out programmatically.

My personal experience for what it is worth is that we trained our users (100+) to deselect the checkbox each time and after months of production, we have relatively few listings.

We migrated five weeks ago so the additional portal  listings are still a management  / training issue. Having solved the Portal Deletion issues earlier today, we at least have a solution for deleting the unwanted listings. I'd love to have a more proactive solution (disable add  Listing or auto delete  listings) but will see if we follow your pattern.

I'm hesitant to go the "customization" route based on pre-migration experiences with non-standard changes we made to our test portal. I've set up a local test box and may implement the custom changes there for testing purposes, but given the current "no customization" constraints I find myself, I doubt it will ever make it into production.

Listings, the bliss and bane of SPS...

I'm guessing that the only kind of documents Microsoft anticipated
people would upload into Area document  libraries would be the final,
unchanging, enterprise files that everyone would need to be able to
find. Documents that do not require a Listing would be uploaded into
document libraries that are in a WSS Webs.

That said, I'm guessing that you could uncheck this checkbox using some
farm-level or site definition-level JavaScript. Let me know if this is
of interest and I'll research it further.