For the month of August, HILL, HDSN, and BMAS were the most active traders on Level II, NITE was rarely seen. Yet if you look at the volume report for August you will see that NITE had by far and away the largest trading volume. So basically NITE is using the other MM's as "fronts" to do their trading for them.
As NITE's trading practices are well known throughout the industry as "questionable", who knows what other kinds of monkey business these MM's are up to?