bug#21844: `sort` behavior unstable based on neighboring elements ?

[Mike Frysinger]

i got this bug report today about sort mismatches.  the order of the
inputs changes the order of the outputs which surprised me.  but it
might be a nuance of unicode collation i'm not familiar with ?

$ printf '%s\n' aarch64 abc zed | LC_ALL=nb_NO.UTF-8 sort -u
aarch64
abc
zed
$ printf '%s\n' abc aarch64 zed | LC_ALL=nb_NO.UTF-8 sort -u
abc
zed
aarch64

why aren't the outputs here the same ?  a nordic user pointed out
that aa is an alternative for å which comes after z, which is fine,
but that doesn't explain why the output isn't the same here.
-mike

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