The teeth are the hardest substances in the human body, how come a soft tongue remains safe amidst it?

Sometimes it doesn't and I bite my tongue. Worst feeling ever :(

As posted above, safe as long as it stays in its usage territory.

I've bitten my tongue so many times that I've had it trained in kung-fu. It's already a white belt (!) and is becoming quite agile at ducking and weaving. If it works I'm gonna get my cheeks trained as well. They don't often get a nip but once in a while they get too close (they're quite nosey, for cheeks) and that can be painful.

It does not always succeed. but mostly I agree: it is pretty good at getting away when the Jaws start to close. ;-)

I guess it is a shortened feedback loop where messages from the jaws that they are half-closed now, get sent straight to the tongue (without even reaching the brain for processing) so the tongue can get a move on.

I would disagree ... I've know people who's mind are set in concrete ... Never had a new thought in their life

Sometimes they don't.  Bad fitting dentures that rub against the tongue can cause problems. 

cause god made it that way

Because they only surround the tongue.

And they only nip the tongue as a warning to it when their boundaries are crossed inappropriately.