I was kidding...but I was also thinking of the thread where people were discussing big vs little endian and the idea that since nobody uses big endian any more, it's not necessary to allow for it.
Endianess only matters for how numbers are stored in memory, but operations like bitshifts, boolean operations and arithmetic happen after the number has been loaded into a processor register, so endianess doesn't matter.
Even if that wasn't the case, flipping a two's complement integer requires only negation and addition (as you showed), and those don't really depend on data layout.
The endian-ness is only the in-memory layout of the bits and has nothing to do with how VALUES are treated. 1+9=10, regardless of how those values are stored, similarly 1<<9=512, regardless of how the CPU internally arranges those bits. The same holds true for inverting the value, the internal arrangement of the bits is irrelevant.
Really you only care about endianness when you fail to treat numbers as numbers, for example by treating them as bytes.
