Possible compromise: let initdb accept en_US, but have it spit out a
warning message:
NOTICE: initializing database with en_US collation order.
If you're not certain that's what you want, then it's probably not what
you want. We recommend you set LC_COLLATE to "C" and re-initdb.
For more information see <appropriate place in admin guide>
Thoughts?
regards, tom lane