Okay, so to go into more detail:

The naive version I mean goes something like "In the future, the universe will have amplitude spread across a lot of states. But I only exist to care in a few of those states. So it's okay to make decisions that maximize my expected-conditional-on-existing utility." This is the one that's basically evidential decision theory - it makes the mistake (where "mistake" is meant according to what I think are ordinary human norms of good decision-making) of conditioning on something that hasn't actually happened when making decisions. Just like an evidential decision theory agent will happily bribe the newspaper to report good news (because certain newspaper articles are correlated with good outcomes), a naive QI agent will happily pay assassins to kill it if it has a below-average day.

The second version I was thinking of (and I'm probably failing a turing test here) goes something like "But that almost-ordinary calculation of expected value is not what I meant - the amplitude of quantum states shouldn't be interpreted as probability at all. They all exist simultaneously at each time step. This is why I have equal probability - actual probability deriving from uncertainty - of being alive no matter how much amplitude I occupy. Instead, I choose to calculate expected value by some complicated function that merely looks a whole lot like naive quantum immortality, driven by this intuition that I'm still alive so long as the amplitude of that event is nonzero."

Again, there is no counterargument that goes "no, this way of choosing actions is wrong according to the external True Source Of Good Judgment." But it sure as heck seems like quantum amplitudes do have something to do with probability - they show up if you try to encode or predict your observations with small turing machines, for example.