In this article it would have been fine to use singular ‘they’ especially since each fictive person is really a group of people, so even read as plural ‘they’ works.
Oh man I wish these were in widespread use. It would simplify things greatly for everyone. I kinda wish HN just started using them and it spread out from here.
There are a bunch of different proposed gender neutral pronouns... which is part of why no one particular set has caught on yet.
I use 'singular they' because at some point 'one' started to connote pretentiousness. I don't see how Spivak pronouns solve that problem, but this off-topic sub-discussion has convinced me to go back to using 'one' (for disambiguation's sake).