The rumours telling about any reason for this chapter's length are very diverse. They also speak of 4 extra short stories in Jump SQ, so some series had to shorten their chapter lenght, D.Gray-man being one of them. I just hope that, whatever the reason, the December chapter will make up for it. BIG TIME!
I gotta agree with SA, though... Kanda was hilarious this chapter. |D
But 208 will be one of the better chapters of DGM for another month, at least.