Well, vi is 6 in roman, m is 1000 though. Something about some sort of xor with the digits '1000' and 6 maybe? 0666? Anyways why they would say that is because they don't like it.
That refers to vi, which vim is based on; the 'm' is meaningless here. "vi vi vi" is "6 6 6" (the number of the beast) in Roman numerals. It's an emacs people joke.