The double crescent moon emblem is probably gone for good. The first time for it to be gone was in Halo 4 and I am sad to say I’ve lost hope for it’s return, as it has been a favorite of mine. I hope no one else is missing it, but I do know there are other “legacy” emblems missing, too. My condolences friends.
I I think it’s a bit rediculous that you unlock emblems which were permanently available in all previous halos, I agree, the double moon will be missed.
Same with the Katana.