The majority of this discussion seems to focus on exit marker/separation of buddy in a clear vis situation. There are instances where this has been in diminished/zero vis......... writing a note is not going to work there.
I really would want to plan for the worst case scenario,because when Murphy strikes there are usually other things occuring. When the original occurence happened there may have been clear viz,but in the process of searching,panic,etc that clear water will become very turbid in a hurry. Hence,any navigation marker placed the wrong way is a hazard to all in the cave.