What's with the downvote? I understand the implied subject, but this part:

n = 2 is valid again as the imperative, this time with a subject: buffalo. That is, "Buffalo buffalo" means "You should harangue some bison."

is wrong. The two "buffalo" are the verb and the object. Neither of them is a subject.

The subject (you) is implied by the imperative.

n=2 could also mean "Bison do harangue."