Dang, do I ever love DFW's rambling. It's so enjoyable compared to everyone else's rambling. I have always wondered why he uses the word 'which' in a way that

Dang, do I ever love DFW's rambling. It's so enjoyable compared to everyone else's rambling. I have always wondered why he uses the word 'which' in a way that nobody else does, as in: "...he had to eject, which basically means setting off an explosive charge that blows your seat out of the plane, which ejection broke both McCain’s arms and one leg and gave him a concussion and he started falling out of the skies right over Hanoi." The second 'which' does not seem grammatically correct to me, but he does it _all the time_, and he probably knows the rules better than anyone. I assume it's a archaic form that he was the last holdout for?