I don't get it - how come returning sitefinder for
ToAscii(feññer.com) where feññer.com hasn't been
registered is worse than returning sitefinder for fenner.com
where fenner.com hasn't been registered?
If your client doesn't implement ToAscii(feññer.com) correctly you will
end up in sitefinder instead of getting NXDOMAIN when you have
registered the correct ToAscii(feññer.com).
My view is that to find that your client is doing the wrong thing,
NXDOMAIN is a better signal than sitefinder. Else, the fact that you
end up in sitefinder will be a general signal that something is broken.