this is not just a minor implementation detail. You are
talking about introducing a completely different semantics for
$0-symbols. Global symbol atoms, as they are defined currently,
are immutable entities. Any Pd object may transparently store
them, retrieve, etc.
that's exactly, what concerns me most ... on the other hand, a $0-symbol
that's $0 is connected with a canvas that doesn't exist any more can't
be seen as valid any more ... the question is how to handle this ...