Thanks for the criticism.

summary: If, hypothetically, I tried to catch a terminal-velocity bowling ball with my face, your theory says I would experience the bowling ball doing nonfatal damage and then stopping just before killing me, and my theory says I would experience changing my mind and getting out of the way of the bowling ball. It looks like our key disagreement is whether Quantum Immortality only operates over short timescales. You say it only acts in an instant, and I say it acts over long time intervals as well.

longer argument: I'm not convinced by your argument yet. Specifically:

1) I agree that two worlds may be very similar or very different or many places in between. However, my consciousness observes exactly one world at once. Do we have a disagreement about reality, or only about word definitions?

2) I agree that splitting events produce massive numbers of worlds (I have no idea how many, but I'm guessing no more than the volume of the Universe divided by the cube of the Planck length). Does this invalidate my argument (that I'll live forever without appearing to get lucky)?

3) I agree that the likelihoods are a sum over various paths whose magnitude ranges from approximately 1 to approximately 0. I also agree with your intuition that if I ended up in a situation with a high-velocity bowling ball partially inside my head then my survival paths are much much less likely than my death paths. However, my argument is that Quantum Immortality works backward in time, if that makes sense. For example, consider all the ways I can walk through a bowling alley -- a 10-minute-long time interval. Quantum Immortality means I will not experience death during that 10 minutes. Looking at all of the different worlds in which I don't die in the bowling alley, it's most probable I'll find myself in one where I walk safely and nothing weird happens, and really really improbable that I'll throw a bowling ball straight up in the air and then try to catch it with my face and then have the bowling ball spontaneously lose its momentum right before impact. This looks like where we disagree. This is clearer in your next point...

4) I'm kept off of those doomed states by Quantum Immortality. I disagree with you here, and I'll make two arguments why...

4a) My conscious experience already averages over large lengths of time relative to quantum processes. The brain runs at about 10Hz. In the time it takes for one neuron to fire, many many quantum processes have time to happen. Since my consciousness only collapses the universal wavefunction once every 1/10th second, I see no problem with looking at the problem as if my consciousness only collapses the universal wavefunction once every 10 minutes, or once every lifetime.

4b) When I look at the real world, it looks like I'm kept away from doomed states. Why was I so ridiculously lucky as to be born in the current era, where human immortality is a possibility for the first time in history? Timeless Quantum Immortality provides an answer: because it's more probable that I'll live forever from the World I experience now, than it would be for me to live forever from most other worlds. Being born an ancient Sumerian or a dolphin would require many more improbable events to get me to immortality. Being born in a post-Singularity culture where immortality already exists would require a more complicated Universe. My existence looks like it's one of the most likely ones of the set of all possible Universes in which I don't die.

4c) I go to sleep (lose consciousness) and wake up again. QI seems to predict that I would never fall asleep, because I stop observing when I'm asleep and so I couldn't observe that instant. Timeless QI has no problem with me falling asleep and then observing I'm alive and awake hours later.

5) QI is all about the timeless perspective because it requires looking at worlds splitting into other worlds from a perspective outside of time. I'm just doing what regular QI is already doing, just on a longer timescale.