You might like to read, "maps of meaning" by Jordan Peterson. He proposes that meaning sometimes will come from the stories that we tell help to form the meaning that we make for ourselves. All stories help us with meaning.
Yep.
And, in the Maps of Meaning lecture series, Peterson gives a shout-out to Rowling's Harry Potter series as being an excellent example of a retelling of an archetypal myth. So, it was a good choice of material for Yudkowsky to use as he did.
I never thought about it this way but it does seem to serve the same function. As far as I know it wasn't deliberate but it did likely happen independently for the reason you reference.
Using mythology to illustrate philosophical points has a lengthy tradition prior to Sartre. Achilles would have been a mythological figure by the time Zeno of Elea demonstrated the impossibility of motion by imagining a race between Achilles and a tortoise. And, in Phaedrus, Plato imagines a conversation between Thoth (from Egyptian mythology) and the Egyptian king Thamus to make a point about literacy.
I'd be surprised if Yudkowsky has read Sartre. But it's a natural thing to do. Harry Potter is (unfortunately) the closest thing we have to a national epic we have these days... well, an Anglosphere epic, but you get the idea.
If this is the sort of thing you're interested in, you might want to read Benedict Anderson's book Imagined Communities.
Am I the only one who sees obvious parallels between Sartre's use of Greek mythology as a shared reference point to describe his philosophy more effectively to a lay audience and Yudkowsky's use of Harry Potter to accomplish the same goal? Or is it so obvious no one bothers to talk about it? Was that conscious on Yudkowsky's part? Unconscious? Or am I just seeing connections that aren't there?