Wei, suppose I want to help someone. How ought I to do so?

I don't know. (I mean I don't know how to do it in general. There are some specific situations where I do know how to help, but lots more where I don't.)

Is the idea here that humans end up anywhere depending on what arguments they hear in what order, without the overall map of all possible argument orders displaying any sort of concentration in one or more clusters where lots of endpoints would light up, or any sort of coherency that could be extracted out of it?

Yes. Or another possibility is that the overall map of all possible argument orders does display some sort of concentration, but that concentration is morally irrelevant. Human minds were never "designed" to hear all possible moral arguments, so where the concentration occurs is accidental, and perhaps horrifying from our current perspective. (Suppose the concentration turns out to be voluntary extinction or something worse, would you bite the bullet and let the FAI run with it?)