Strange locale dependent sort behaviour

[Petter Reinholdtsen]

I just discovered something strange with the handling of eth with sort
-u and the no_NO locale.  Notice how the lower case ð disappear after
'sort -u' filter the output:

  % echo -e "Ð\nð\na\nA"|LANG=no_NO sort -u
  Ð
  A
  a
  % echo -e "Ð\nð\na\nA"|LANG=C sort -u
  A
  a
  Ð
  ð
  % echo -e "Ð\nð\na\nA"|LANG=nn_NO sort -u
  a
  A
  ð
  Ð
  %

This is with the locales from glibc 2.2.5 (Debian Woody).  Is this
normal behavoir for all characters not listed in the LC_COLLATE
section of a locale?