Hire Good Writers
gettingreal.37signals.com
gettingreal.37signals.com
So it's no surprise that they'd write a post about liking writers. After all, it's just human nature to like someone that closely reflects one's self.
They aren't blog posts. They're "chapters" in a "book". Your confusion is completely justified, though. People who would try to pass off blog-style entries as chapters in books should not discuss "good writers" much less try to determine what exactly good writing signifies.
They are different art forms.
Otherwise we should be looking for greeting card writers.
LOC comparisons for literature is a goofy idea.
Candidate A doesn't know what a binary tree is--but he knows how to properly stamp out dangling participles.
Candidate B knows how to code.
The first rule of a good writer isn't clarity, style, correct semicolon deployment, etc, but is rather saying things that aren't patently false.
The thing about good writers is that they understand communication at a higher level than most people, because they practice it consciously rather than subconsciously. Therefore, a good writer is necessarily a good learner (the read-side of communication), and, assuming no specific mathematical-related learning difficulties on either side, would probably become a better programmer than the "actual" programmer.
I like your second paragraph very much. A guy who'd been teaching programmers at a technical college for a long time told me that the only predictor he ever found for programming aptitude was a combination of math and English skills. Neither one in isolation was correlated with success, but if you were good at both then you were more likely to do well at programming.
But if I have to choose between Bill Shakespeare and an MIT grad for a programming position, guess who I'm hiring, despite 37signals' crappy, abbreviated, unsupported advice?
Programming is writing, so good programmers are good writers by definition. I think the relationship between writing code and writing prose is a rich and interesting one. For example, each involves a great deal of reworking and editing before it is gotten right. Each requires the ability to think clear thoughts and to organize and express them. Each is about communicating to others (even when the only 'other' is yourself later on).
I've observed that programmers whose writing I have difficulty following tend to be programmers whose code I have difficulty following. The converse is also the case. So I think the point is a good one, even if I wouldn't express it the same way. And of course it doesn't mean I would hire Andrew Sullivan or Paul Graham to write me a binary tree - oh wait :)
The people who were really good software engineers were usually great writers; they had tremendous ability to organize their thoughts and communicate. The people who were sort of average-quality programmers and had trouble thinking about the larger picture were the ones who couldn't write.
I wish I had remembered this earlier. That the point was articulated by a sharp observer like Greenspun illustrates that it deserves attention beyond the rather glib formulation in the post we were discussing.