I thought they asked for your HN username. What else would they do with it?

not parent. I bet they do not, however I think you implicitly agree by providing it on the application. Maybe in the case of partners being on the fence, ect, but if not out of privacy probably strictly out of time and number restrictions. That said, they always speak about how incredible their internal software is YC and HN has solid management & spam reduction software. I wouldn't be surprised if they filter for some internal criteria in an automated fashion.

To be fair, using the word 'privacy' implies that those conversations were private in the first place. In my opinion, there is nothing 'private' about verbally abusing (or whatever else lead to the report) a stranger on the internet on a 5v5 chat (plus any potential spectator).