HELLO! This all sounds like 'magical thinking'.
Putting a note saying "I have a list of all contents"! This is going to be most useful in Paris or Frankfurt.
I believe in thinking defensively when traveling, being sensible enough to leave precious jewels or heirlooms at home, and selecting good, serviceable and practical luggage that suits your style, wallet, and travel needs.
The rest--'tape around the zipper' etc--is like pilgrims going off on a pilgrimage and wearing certain talismans and other things to ward off evil. A serious thief knows how to get into luggage--and if the zipper is taped, it makes sense that he or she would rip the bag open with a knife.
If you don't want it stolen or lost (or left behind in a hotel room) don't take it.
Writing a note to a robber: go ahead. Do anything 'magical thinking' to give yourself peace of mind, or to feel that you have done 'something' to protect yourself or feel in control. Best advice: if it's precious and irreplaceable and your care about it, carry it with you, wear it, or leave at home (in a safe).
Exactly the kind of comment the Addendum should have taken care of.
I do think the tips are all worth considering based on the circumstances. Luggage thieves are looking for easy opportunities. If you make it just a little harder, the chances are better that they will move on to the next bag.
When the pickings are really easy, temptation makes the thief. Even I was tempted for the Vuitton bag.
Just kidding, not my style, but would have been easy enough.
Till