There is a very distinctive note that I have encountered in most Mont Blanc scents, especially L' Homme Exceptionnel, in Rochas Lui and in Givenchy Incense. In my nose it is sharp, metalic, almost feels like ether but it is not apparent only during the opening but stays almost throught the entire wearing. It has a visual analogue to a sharp steel blade to me. I used to find this note refreshing but for some strange reason as my taste evolves I find it almost unbarable. I was wondering what substance or substances create this note?
I've been wondering the exact same thing! This is exactly what I sense in Lui. It's great that somebody else smells this.
One theory that I have is that this is either the "chypre ghost note" or something like it which arises from a similar phenomenon. See the discussion of the chypre note in this thread. Based on reviews, only some people are perceiving a chypre aspect to the scents you mention. Normally, oakmoss is required to make a chypre, but none of these are described as being oakmoss-dominant scents. There are supposedly now chypres without oakmoss, although purists will scoff at that. Nevertheless, if chypre is a more general phenomenon, and can be achieved by the harmony of other notes relative to human olfactory receptors, then it is possible that other notes are being used to create a similar effect.
One possibility is an aromatic note such as sage, which can present (pun intended) as medicinal. Another possibility is that the sharp aspect of some cedars is being used as one component of a chypre-like note, along with citrus, etc.
I would be very interested to know if others are experiencing this "sharp" aspect, and to what they attribute it.