Unforgiven

When people ask about the Dark Angels, how do you answer with out telling the secrets, i mean the codex is an awful example it literally spills the beans in the first story. Imagine in universe so whats your chapter called... unforgiven for what, it doesn't mater sounds like heresy! Traitor! We need better writing, explicitly tell the rituals that hint at the dark past don't hand wave them away, it's like someone published the outline of a consept of an idea super under cooked