I read it this year, too. It's a fun read, but I wouldn't recommend anything past the first group of articles (that is, don't bother with "Five Five Five Five Five"). The ideas are good, to be sure, but the overall arc past that is pretty weak.
Their usage of "their" aligns with how English has been used for centuries (Wikipedia says 14th century), but more importantly the author's writing was the topic of discussion not their gender.
Policing other's pronoun usage is ideological, but that's your argument, not theirs.
Obviously, that is: statistically, all involved here (the SCP author, the HN commenters, you, me) are men, so saying "he" is very likely correct. If by chance someone here is nonetheless a woman she will probably speak up.
'Their' is practical not ideological - Sam could be Samuel or Samantha, and I didn't know which. Also, bring up the use of 'their' for unknown gender with Shakespeare and Austen, who both did it.
The only one being 'ideological' here is you, getting worked up over basic grammar that's been around longer than Modern English. Go out and touch some grass.
Yeah, the first half or so is a blast, but there’s a point where I feel it drops off quite a bit. (For me, I think it was when the POV changed to Adam.) Still worth a read, though!
