In a Show Case, post constructive criticism that has nobody has not yet.
Use proper grammar, but you are excused if you are Chinese or Japanese:
So are you Chinese or Japanese?
Or maybe I am Chinese or Japanese, because I literally cannot make sense of that first sentence.
I think he just forgot to add "posted" at the end of the sentence.
Even if you add posted at the end, it still have an extra "has" and "not", and even
"In a Show Case, post constructive criticism that
has nobody has
not yet
posted."
is pretty forced.
I think what he meant to say was
"A Show Case post should be original and constructive."