You're joking, right? Here's another situation for you:
6768033e216468247bd031a0a2d9876d79818f8f == sha( 0000000000000000000000000000000000000000 )
Here, knowing the output (6768..8f8f) tells us what the input was (00000..0000)! There are
2^160 situations like this, not just one or two. As long as the only way to know the input for
some particular output is to try all the inputs, the hash is not broken. What difference would
it make if some unique value would both be the argument and the result? I fail to see any.
As far as I understand, no one has ever stated that a crypto hash may never produce the same
output value as its input value. That's why I was asking in the first place.