The teacher said to him, "I told you the right thing. The very fact that you know simultaneously all the mental modifications was adduced by me as the reason why you are eternally immutable".
This has been the subject of much reflection for me manana (reflecting) and nidhidhyasana (meditation). What I mean by this is the holding in the mind or making the context of my ruminations the immediacy of consciousness. Is the assertion that mental modifications are immediately known otiose or not informative. Mental modifications are those states of awareness that we are immediately aware of by definition. Daniel Dennett speaks of fame in the brain. Those states (vritti) are merely the most salient of our brains function. Information is being processed in an unconscious way and what we become conscious of is merely the last stage that wins out so to speak. They are famous i.e. well known. Only when the activity that is beneath this level goes wrong do we come to know of it.
I feel that there is an important insight in Dennett's view and it moreover does not contradict the advaitin view of mental activity. Recall that in the preamble to the B.S.B. (Brahma Sutra Bhasya) Sankara does not concern himself with the psychological theory of how superimposition (snake/rope adhyasa) takes place. It is the end result i.e. the mental modification/confusion, that is important. There are routines that are 'beneath' consciousness but that is not the point. Fame is the thing.