Most math kills you quietly, neatly, and cleanly, unless the apparent obstacles to distant timeless trade are overcome in practice

Will mentioned a couple of other possible ways in which UFAI fails to kill off humanity, besides distant timeless trade. (BTW I think the current standard term for this is "acausal trade" which incorporates the idea of trading across possible worlds as well as across time.) Although perhaps "hidden AGIs" is unlikely and you consider "potential simulators" to be covered under "distant timeless trade".

I don't spend much time talking about this on LW because timeless trade speculation eats people's brains and doesn't produce any useful outputs from the consumption; only decision theorists whose work is plugging into FAI theory need to think about timeless trade

The idea is relevant not just for actually building FAI, but also for deciding strategy (ETA: for example how much chance of creating UFAI should we accept in order to build FAI). See here for an example of such discussion (between people who perhaps you think are saner than Will Newsome).

not to mention the horrid way it sounds from the perspective of traditional skeptics

I agreed with this, but it's not clear what we should do about it (e.g., whether we should stop talking about it), given the strategic relevance.