For what it's worth, and assuming I haven't misunderstood, Acorn's RISC OS had/has the concept of thing-which-is-a-file-and-directory. There were programs that made things like zip files behave as if they were a directory, and IIRC when another program asked the OS 'is this a file or a directory', it returned a bitmap where (say) bit 1 signalled 'this is a file' and 2 'this is a directory', and both would be set. Naturally this slightly broke programs that were written before they added this feature which just checked for a 1 or 2 value, but I don't remember it causing too many problems.
Not trying to argue a case for or against making the change in Linux here, just thought I'd drop this in...
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