I know. I wanted to rule out a different set of facts about immortality than there were in the story, because deathism under those conditions would basically be a different position from deathism in the story, or deathism in real life. Changing the subject of the argument to make a side right is not steel manning that side, and it's not required by any reasonable rules of fairness.
Also, does it really matter if the deathists are too wrong in our eyes to make a good story? I would think that they just have to have a reasonable position in they eyes of the audience. By making this something of a genuine conflict from the perspective of LessWrongers, maybe you've made it settled in favor of deathism from the perspective of a large fraction of the readers.
Thermodynamics isn't the obvious objection IMO, it's the big rip. Alicorns may be able to create matter around them, but perhaps they are the only things that can't be torn apart by expanding space. And maybe they can almost be torn apart, but not quite. So an eternity of feeling like you're suffocating, being almost torn apart, and almost frozen, and being alone awaits every alicorn eventually.
Hopefully the physics in this world are sufficiently dissimilar from real life that that won't happen.
By making this something of a genuine conflict from the perspective of LessWrongers, maybe you've made it settled in favor of deathism from the perspective of a large fraction of the readers.
Entirely possible. I might edit that detail out.
I recently published Mortal, a novella-length My Little Pony fanfiction meant to introduce anti-death concepts to an unfamiliar audience. Short description:
This is a character-driven melodrama. It's not particularly rationalist, but it's very, very transhumanist. Unlike, say, Friendship is Optimal, I wouldn't necessarily recommend this one to people who don't already know the source. It assumes familiarity with the characters and the world.
I am going to talk about how I put together the story and how people reacted to it. This will contain spoilers.
This line exists so you can break out of the automatic "read everything on the page" mode if you want to avoid the spoilers.
This story was structured as something of a bait-and-switch. I watched the reaction to a previous transhumanist horsefic (yes, there's more than one), and I was struck by how easily readers matched the explicitly anti-death narrative to the "immortality is a curse" trope. Rather than fight against this trend, I decided to work with it. The first act is meant to look like a story about learning to accept the inevitability of death. Starting in chapter 3, I break further and further away from that mold until the protagonists finally rebel against the status quo.
The first chapters got a lot of people invested who I suspect would've been turned off by a less familiar opening. Once I was into the third act, I stopped being subtle and used every trick in the book to make the pro-death characters look like the unreasonable ones. Judging by the comments, there's no shortage of readers who were angry at having their expectations flouted, but quite a few seem thoughtful, and some explicitly changed their mind on the subject.