Also just differing levels of relevance. You don't talk with a businessman or investor or famous people in general because of their writing; if you made a list of relevant skills, 'proper spelling when quickly texting from a phone' surely doesn't crack even the top ten thousand skills. In academia, on the other hand, writing a formal application properly is a core skill.
I would have to consider carefully if I thought I was a high-enough quality candidate that it would be interpreted as a countersignal rather than a signal.
If I, gwern, specifically, were to apply, I might; because I know I am widely read on HN and I've talked with any number of YC partners etc, and they all know I take care in writing, and so me not capitalizing is a deliberate message rather than laziness or incompetence. They may or may not appreciate the message, but they won't infer the usual things, at least.
If I were anyone else and my application just one of thousands in the flood? You'd better believe I'd capitalize and spellcheck my YC application: https://gwern.net/blog/2023/good-writing
