I'm tired of messing around with this. As far as I've been able to
determine, someplace between RH6.0 and 6.1 'sort' began to automagically
use -f. I can't find any way to turn that off.
It doesn't default to -f, it just has locale support enabled.
Because it turned out to be confusing, we've disabled locale support again (it's
enabled with -l). Get the textutils package from 6.2beta or rawhide.