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It is a singular "we" instead of the plural "we".
"iu" are the best therefore it retains the singular of "I" and "YOU" are the best while meaning "WE" but emphasizing the singularity of the two individuals.

iu are the best on povdmm4...iu fight the nasty chavs that shit on the streets...I think iu have big ballz!
by Sam and Stu August 26, 2008