<p>I think the point of the 500-word limit is not to see how well applicants pay attention to nitpicky details, but to give them a benchmark for how long an essay should <em>feel</em>. If your essay is only 400 words but makes the adcom shake its head and say “WHY GOD WHY ISN’T THIS ESSAY OVER YET”, that’s probably a problem. If you have a 600 word essay that makes them say, “wow, I can’t believe Applicant X said so much in so few words,” that’s a good.
Or maybe that’s just what I’d like to believe because I can’t get mine down from 550.</p>