[davidu]

They've been clear that they do look at your HN posts and comments, etc.

It may or may not be used for ranking in specific, but it's definitely used and they've always been upfront about that when asked.

[idoh]

Also, they use hacker news to communicate to applicants. I applied a while back, and one day while browsing I got a message through HN, something like "pg has a question for you" in the header bar. Clicking through is the question, and place to put the answer.

Basically, there's a whole messaging system in hacker news that most people don't see.

[markbao]

Yeah, this is known :) but an algo that incorporates HN karma wouldn't be the best thing :P