That would be interesting. As imperfect as my grammar and spelling are, I know that when I have a stack of resumes on my desk to review, the first pass weeds out the ones with grammar/spelling mistakes. Applying for a job is too important of a task to make avoidable mistakes like that. If you have not taken the time to make your resume perfect then you are likely to do sloppy work in your day to day activities. I would apply the same filter to a YC application. If I ever find myself working up an application for YC, I would spend the time and money needed to make sure every bit of that was correct. Now whether it should be formal or informal or what have you would be a big mystery. I would tend to lean toward formal in something like that. But perhaps not so formal that I come off has a robot. You can't trust robots.