I, for instance, do not think it's okay to kill a copy of me even if I know I will live on

Not OK in what sense - as in morally wrong to kill sapient beings or as terrifying as getting killed? I tend to care more about people who are closer to me, so by induction I will probably care about my copy more than any other human, but I still alieve the experience of getting killed to be fundamentally different and fundamentally more terrifying than the experience of my copy getting killed.

From the linked post:

The counterargument is also simple, though: Making copies of myself has no causal effect on me. Swearing this oath does not move my body to a tropical paradise. What really happens is that I just sit there in the cold just the same, but then later I make some simulations where I lie to myself.

If I understand correctly, the argument of timeless identity is that your copy is you in absolutely any meaningful sense, and therefore prioritizing one copy (original) over the others isn't just wrong, but even meaningless, and cannot be defined very well. I'm totally not buying that on gut level, but at the same time I don't see any strong logical arguments against it, even if I operate with 100% selfish 0% altruistic ethics.

When there is a decision your original body can make that creates a bunch of copies, and the copies are also faced with this decision, your decision lets you control whether you are the original or a copy.

I don't quite get this part - can you elaborate?

If it waits ten minutes, gives the original some tea and cake, and then annihilates them, the person who gets annihilated has no direct causal descendant - they really are getting killed off in a way that matters more to them than before

What's about the thought experiment with erasing memories though? I doesn't physically violate causality, but from the experience perspective it does - suddenly the person loses a chunk of their experience, and they're basically replaced with an earlier version of themselves, even though the universe has moved on. This experience may not be very pleasant, but it doesn't seem to be nearly as bad as getting cake and death in the Earth-Mars experiment. Yet it's hard to distinguish them on the logical level.