Interesting, I wonder if it's used in any of the French-speaking countries other than France.
Yes, it's used, but very incorrect in standard French, so, don't learn it.
would bon matin be accepted?
No, in this case, better say "bonne matinée"
Bon matin is awful, as a greeting.
C'mon, what's wrong with nonnankobra's answer??
What's wrong is just that the French don't wish "bon matin".
Bon matin would be used like, "I had a good morning (J'ai ete un bon matin)" Bonne matinee is like bonne journee...it is wishing someone a good morning/good day.
Please note: "J'ai EU une bonne matinée" or "j'ai passé une bonne matinée" (not a bon matin, anyway).
"bon matin" is used in the expression "de bon matin" meaning: early morning.
oh mon dieu! bien sur, merci.