Let me just note some of the main similarities and differences between this 
issue of Unicode compositions and the issue of case-sensitivity in file names.
Differences:

  * NFC and NFD look the same when 
displayed, and most users haven't heard of them and don't expect that a 
computer might treat two 
identical-looking filenames as different.  With letter case, most users are 
aware that some systems treat upper and lower case letters as the same while 
other systems treat them as different, and they learn to behave according to 
the system's rules.


  *The main 
case-insensitive file systems are case-preserving with no "normal form", 
whereas the main system that treats NFC and NFD as equivalent(MacOS) chooses 
one form as the "normal form" and always normalizes the given file name to that 
form.


Similarities:
  * If two Unicode strings differ only by letter case, on some computer systems 
they refer to the same file, while on other systems they refer to different 
files.  The rules are created by the 
designers of the systems, sometimes explicitly and sometimes 
implicitly.  Different parts of a system can have different rules.  The 
same applies if two Unicode strings differ only by composition. 

  * Subversion  interoperates with different systems.  When two file names that 
differ only by letter case are transferred from a 
case-sensitive system to a case-insensitive system, they will collide 
and Subversion shouldhandle thisin some friendly way.  The same applies if two 
file namesdiffer only by composition.

The differences are important, but the similarities are enough that we should 
be looking for some commonality in the implementation.

- Julian

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