Middle-endian FTW!!!! 
 That makes me wonder: was
there any hardware that used an endianness
 such that conversion didn't loop with period 2? 
  Not quite the same thing but
weren't longwords on the PDP-11
 little-endian for the bytes within the word but big-endian for words
 within the longword? 
 
Yes.  As I said in the very next paragraph,
  Conversion between PDP11-endian (0x87654321 stored as
0x65 0x87 0x21
 0x43) and [...] 
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