That was a quick estimate of the timescale where mitigating astronomical black swans becomes worth doing.

This seems to be highly sensitive to the amount of time EAs currently spend on deciding. I think that most people are likely to end up not donating at all if they feel pressure to spend more than 2 hours making a decision - I'm not sure if EAs are selected enough to mitigate that factor.

I also moderately believe that most EAs will not use the extra time very well (e.g. just pouring the extra time into more detailed analyses of two similar causes).

I agree with this on timescales of around 1,000,000 years or so, but disagree with the colloquial interpretation that this is something that would be useful in mitigating the x-risks we currently face.

Alright, I've reworked this part, do you think it is better now?

I think this sentence would be easier to read without the parenthesis around the second sentence.

Shouldn't this be a child of Abstract Algebra?

right, fixed!