This is so useful! I love this kind of post and will buy many things from this one in particular.
Probably a very naive question, but why can't you just take a lot of DHA **and** a lot of EPA to get both supplements' benefits? Especially if your diet means you're likely deficient in both (which is true of veganism? vegetarianism?).
Assuming the Reddit folk wisdom about DHA inducing depression was wrong (which it might not be, I don't want to dismiss it), I don't understand from the rest of what you wrote why this doesn't work? Why is there a trade-off?
This seems really exciting!
I skimmed some sections so might have missed it in case you brought it up, but I think one thing that might be tricky about this project is the optics of where your own funding would be coming from. E.g. it might look bad if most (any?) of your funding was coming from OpenPhil and then Dustin Moskovitz and Cari Tuna were very highly ranked (which they probably should be!). In worlds where this project is successful and gathers some public attention, that kind of thing seems quite likely to come up.
So I think conditional on thinking this is a good idea at all, this may be an unusually good funding opportunity for smaller earning-to-givers. Unfortunately, the flip-side is that fundraising for this may be somewhat harder than for other EA projects.
Can you say more about the 20% per year discount rate for community building?
In particular, is the figure meant to refer to time or money? I.e. does it mean that
(For money a 20% discount rate seems very high to me, barring very short timelines or something similar. It would presumably imply that you think Open Phil should be spending much more on community building until the marginal dollar doesn't have such high returns anymore?)