If you look over the element ratios we measured, you might conclude that our comet particles look more like chondritic porous IDPs than CI chondrite meteorites.
By that, I mean: OK, we assume your superhero might be extra-strong, or might be able to fly or run as fast as a comet, but unless you care about the superhero's personal life, you're just reading a shallow story.
It's possible that when comets hit Earth billions of years ago, elements in the ice were scattered and struck by lightning – a bright flash of light produced by electricity moving in the atmosphere.