This is very much a cultural fit test. If people who use poor grammar are going to drive the author nuts, then as the the person running the company I think he's perfectly justified in treating the candidate as a poor cultural fit.
Additionally, as someone who employs writers as well as programmers, he might reasonably want to hire a programmer who is also a writer for the same reason that you'd want to hire a programmer who also has ops experience: it makes them a more appealing hire for the kinds of problems his startup is trying to solve.
You don't see the problem because you look at it from a different direction.
Hiring good programmers is already hard enough. And you are likely to hire a bad programmer despite having them run through many programming interview sessions.
If you put all sorts of irrelevant criteria in between, you are likely to get people who have mastered the art of beating interviews by specializing in those criteria and diverting your attention from actual issues. Then we all go back and complain why its so hard to hire 'good' programmers.
The OP generated a lot of strong negative reactions. But it also generated some strong positive reactions from programmers who share the author's frustrations and would enjoy working at a place where everyone punctuates impeccably. Like the author, my experience has been that programmers who care about language tend to write beautiful code.
I'm not looking for a job. But if I was, this article would make me more, not less, likely to apply.
I'm an owner at a software dev shop now, and I loved this article. I can't imagine actually using grammar as a litmus test, personally, but it definitely goes into my on-the-spot judgement criteria. I feel significantly less-comfortable working with someone who lacks the critical thinking skills or personal professionalism to be intensely concerned with how they interact with others - and grammar is significantly about that.
If you can't be bothered to learn grammatical syntax, and it's something you've done your whole life, why should I expect that you'll be bothered to pursue perfection in other areas? If you are bothered to pursue it, why should I believe you have a chance at approaching it if you haven't nailed something you've done since you were five years old?
Anyway, I've not taken the time till now to really develop my understanding of this flash judgement I make of people, but it has always really bugged me. I have a friend who some people view as 'redneck' because he's got a bit of southern good-ol-boy in his heritage, but he's been reading books since he was young and it shows. We took a chance on him, brought him in-house, and trained him. One of the reasons I knew he'd become a great developer was because of the attention to detail he gave to everything that he did. It played out extremely well, for us and for him, and that one signal was a huge part of it.
Obviously anecdotal; typical caveats apply. Still, I'd rather live in the world iFixIt's pursuing than the world we presently live in, re: grammar.
EDIT: hilariously, for grammar. I missed a question mark.
Writing skills are clearly a BFOQ for an organization where your entire work product is written; there is absolutely nothing illegal about a writing test for a programming job.
Additionally, as someone who employs writers as well as programmers, he might reasonably want to hire a programmer who is also a writer for the same reason that you'd want to hire a programmer who also has ops experience: it makes them a more appealing hire for the kinds of problems his startup is trying to solve.
In short, I don't see the problem.