Also, he never really says what was wrong with these employees. Vague doubts about "fit"? "Get under your skin"? "Don't mesh"? All sounds like a discrimination or wrongful-termination suit waiting to happen. Anybody who is in any way dealing with HR should know that firing someone requires extensive documentation of actual wrongdoing, not just this weak "feels wrong" crap. I'd be very surprised if that's less the case in Canada than in the US.
This author really needs to worry less about cover letters, and more about why his company is having these cultural-fit problems. Maybe putting "Like to work late?" and "Test your ping pong and foosball skills" on the Careers page doesn't attract the right kind of employees. I'd love to hear what some of those ex-employees found once they got there, especially regarding the little Pocket Napoleon of a COO.