With "some setting" being "loading a logical volume manager or unionfs kernel module, creating a new file system spanning both devices and reconfiguring the entire system to such a deviant use of removable slots", yes. Nested mount points as recommended by convulted won't extend the file system, but the directory structure.

Yes - worse than that, even any unpatched Linux. Volume spanning across removable volumes is a fairly stupid idea - you'd have to strip the system of all removable drive handling, as anything that triggers hotplugging of one device (or both devices in the wrong order) might destroy your data or create a deadlock. Windows does not permit it at all, and in Linux (which is more generous about letting you shoot yourself in your own foot) you'd have to work around all safeguards to make it work...