I might be wrong, so thanks for engaging. You might be naive, but I might be an asshole. :)

But seriously, if I were doing a Y Combinator application, I would make sure that my testimonials were spot on. I would do so because one of Y Combinators' most enduring bits of advice is 'build something people want.'

I'd even equate that to grammatical errors in a website. You're competing for an interview against thousands of the best minds around. Proofread your copy!