So, one last follow-up, perhaps \du or \du+ should show when a role is mapped that way. If I'd seen a clue to this setting that had been made "before I got here" it would have been figured out sooner.
I realize ALTER ROLE... SET... can be used to set many more defaults, and there could be some debate about how much to display with \du[+], but the fact that a role abandons all its privs and adopts a different set seems like pretty important info to surface ;-)
