Ho, I didn't explained myself correctly... Hamming distance is an abstract mathematical concept, not something you use directly. But it is the theory behind checksums.
And as said, I don't know how btrfs does the recovery in particular, only that this particular sentence was not that off from what I understood.
RAID is not directly related to Btrfs, as he answered a few messages later.
So it looks like to be too technical to be answered in a few messages, so I propose to close this and not hijack any more this thread .