As someone who is a regular (permanent?) attender on HN's rate limit blacklist[0], I can say that from personal experience: You will likely not be notified before HN punishes you, but from contacting HN about said incidents, it's generally (maybe always?) a manual process by an irritated HN mod. And if you email them (hn@ycombinator.com) about your apparent ban, they're generally willing to converse.
[0]I was unable to post this comment when I wrote it, and had to wait.