What is a subtle displacement at the moment of the cut? In In the blink of an eye book (page 6), Walter Murch explains that displacements at the moment of the cut should be either subtle or total:


  What we do seem to have difficulty accepting are the kind of displacements that are neither subtle nor total: Cutting from a full-figure master shot, for instance, to a slightly tighter shot that frames the actors from the ankles up. The new shot in this case is different enough to signal that something has changed, but not different enough to make us re-evaluate its context: The displacement of the image is neither motion nor change of context, and the collision of these ideas produces a mental jarring—a jump—that is comparatively disturbing.


As I understand it, all following cuts are total, right?


A cut from a person walking down the street to the same person leaving the elevator and walking to the door of his flat,
A cut from a person walking down the street to the same person turning at the corner of the same street,
A cut from a person walking down the street with the camera showing him from the front to the same person on the same street with the camera from behind,


But then, what exactly is a subtle displacement? A displacement which is neither subtle nor total?

Would a cut from a 35mm shot of a house with a person in front of it to a 50mm shot of the same house and the same person will be considered as a subtle displacement?

I don't recall seeing any subtle displacement in movies. Are they used at all? Are there any well-known examples of such cuts?
Subtle cuts are cuts that are blended such that you don't notice they are occurring.  They are the hardest type of cuts to pull off.  You can do them during a quick pan or if you have a near stationary scene.

The key point that Walter Murch is getting at is that jump cuts, cuts where the viewer is jarred in to noticing the cut, should generally be avoided as they break continuity.  As with any guideline, there are exceptions and in some situations you may want to intentionally jar the audience, but generally, you avoid it by either having a major change in context or angle or you blend it so smoothly that the cut is not noticeable.

For a great example of a subtle cut, look at the boat sinking sequence used frequently in the TV show Arrow (available on Netflix).  There is a shot where they go from being in a cabin there is a whoosh of water as the girl is washed out of the boat and then we are looking at a shot from outside.  While there is no clear cut, a transition was made (though in this case it could also be a total cut as there is a context shift).

You may also occasionally notice subtle cuts in documentaries when the editor is able to make a cut between takes where the speaker's head was positioned in the same spot and so you don't actually particularly notice that an edit was made.  These are only possible when the situation lends itself perfectly to such an edit, but it can sometimes be done.