The crescent could be D. The letter D is like a half moon, crescent. Idk
(￣∇￣") crescent isnt half moon... but the secret about the D, maybe one piece holds the secret of the D clan. who knows. or about the gods island idk ahh ODA what do you have in that brilliant mind of yours.
The cresent moon was the symble for those wano people right? The ones who where on the side of the Kazuki clan.
It could be something else though.
the third world (present) said "half moon echoes through the ages" which does sound a lot like D clan lore
the lore and everything tells us about the prophecy and whats to happen and what has happen and all the good plot... but you know whats even more interesting? one piece. there is no clue about WHAT THE ONE PIECE ACTUALLY even after a decade we know nothing about one piece.
my input after this chapter:
maybe one piece is a key/power to go against the shadowy bastard?
what if the devil fruits actually a gift from the forest god or something?
those of the crescent moons (no idea who dis about) and the full moons, is it about the minks?