Hmm. I was aware of the bonuses-from-the-same-spell rule before, but what still puzzles me is the wording of the spell. Firstly, that rule says usually, not always, and I'm not sure that it "takes precedence" over naming conventions.
And the spell specifically says +2 Strength. In the same book with spells such as Cat's Grace, which grants "an enhancement bonus to dexterity of..." If it were a slip-up, it should have been errata'ed. If not, then it's meant to stack.
Now the temporary hp from the spell, I'd think, wouldn't stack. I've seen endless debates regarding Vampiric Touch, vampiric weapons, and Claws of the Vampire, and to the best of my knowledge, they always wind up stating that these temporary hit points overlap, but don't stack.
The +1 caster level is hard to say. I'd probably go with the "same spell" clause here, since, like Haste, it's providing a non-bonus type effect. Three Haste spells won't get you three partial actions, and three Death Knell spells probably don't get you +3 caster level. Then again, as Death Knell is so hard to use, perhaps it was supposed to.
Of course, if any of the effects of Death Knell stack, then the bucket o' snails problem comes up. But that comes up with lots of game mechanics, so it's just something the DM would have to nix outright (the snails, not necessarily the stacking).
Any other opinions?
