Fanfic creates its own canon, and it can make its own twists and turns. A spoiler is a spoiler, no matter where it comes from. And a death can be part of a fic without the fic being ABOUT the character's death.

(also, if a fic is labeled A/B deathfic, it's pretty obvious that either A or B is going to die.)

Personally speaking, death is the one thing I never label in my own fics, and I've gotten some good reactions out of it, so I figure I'm doing something right.