The sort utility defaults to folding lower case to upper case. This is
only supposed to be enabled when the -f flag is given, and there is no
means to turn it off. This in turn breaks the use of ctags to make tags
files for vim to use since vim requires sorted tag files that don't fold
lower and upper case letters when sorting.
It's not a bug, it's a feature.
sort now respects locales.
What you want to do is setting LC_ALL=C before using sort.