Well, I've had my account for over 2500 days, and my karma only yesterday broke 1000. But I read HN daily, and feel part of this community.

I just only comment when I feel like I can add something to the conversation, and always pause before commenting (stops me from getting into flame wars)

So age of account should have some say, or at least if they can see how often you read and vote for stories and comments here.