I think Quora handles this better than HN. It gives you the option to be completely anonymous on a case by case basis, reap the benefits/upvotes even when you are anonymous. Most people on HN/Reddit resort to throwaway accounts when they want to be completely anonymous and not tarnish their username, even though that username has no connection to a real world ID.

People/usernames are brands in online discussion, so the way we generally weigh people's opinion is affected by those brands, which is kind of a function of their comment history and any IRL connections. Say, if the username is 'pg', even if it's a hit-and-run comment with not much thought put into it, you view it differently.