I read:

BTW, what does Pd right now if there are two identical objects?

there is noc such thing as two identical objects once [name~] is loaded all references to it will call name_tilde_new() pd will simply not try to load another object (or abstraction) wiht that name.

Does the one win that is loaded into Pd first?

of course see above

(I gues the order is Pd core objects -> libraries -> single externals -> abstractions ?)

no the order is the order of your path and lib flags (of course the core objects will always be there since they are loaded at startup) and (at least for abstractions) . comes first in the search path)

regards,

x