> Maybe I am wrong, but... is it possible to mount two (or more) devices
> to the same directory?

Given your experience, I would have to say yes.   But more to the
point, what you see is not a bug - it's a feature.   If you were doing
a union mount, for example, it would be a real drag if you couldn't do
it right on top of an existing mount point.

			       _MelloN_