I think one thing that's important to consider is that Preservation says in SH, "I've never been able to kill," which to me, sounds like something in his past that he's refering to. Maybe something that haunts him even.
Oooo, now I'm thinking about it, it would be really sad if he were talking about Ati. His Shard forced him to lock his friend away rather than put him out of his misery. I don't know, thinking about those two gives me chills. It'll be really sad to read about them later knowing how their story ends.