Locke always fakeLocke
What if when Locke came on the island, he died, and the MiB always impersonated him? It would explain why he could miraculously walk. It could be inferred, if this is true, that he somehow manipulated/brainwashed Walt and that is why Walt is such a mysterious kid. Locke always seemed to be against Jack. Also, Locke always had a plan for “the island,” he always knows what to do.
When Richard went to see if Locke was special off the island, he did not see any unique characteristics. Maybe this is because Locke is not special. Locke was dead as soon as he got on the island and it is MiB.