if a user is downvoted>n times, delete the comment with added penalty factor. this would keep the content clean forever.
Despite the downvoted comment being hidden, it almost stands out the elitist comment(and nowadays the chain of explanations growing usually offtopic)
Could we restrict users to one user per ip? I sometimes suspect people using multiple ids to upvote their comments/posts. There are some posts way out of HN league that get upvotes within minutes from the new page (even the spammer ones).
Would it be hard to have new users moderated? One way is for new users to write few lines about themselves. Moderator would look for human(no-spam) and genuinity.
Show a warning or part of content from http://ycombinator.com/newsguidelines.html upon submission of a post or comment - until they attain their downvote karma rights.
One liners like 'i like it too' should be deleted. Perhaps there should be a minimum amount of words for a reply or a warning telling the user to verify if he really wants to post.
Link searchyc.com on top of the page beside 'submit' - new users don't know of this awesome search site. While there is a search link at the bottom of the page, I wouldn't be using it more than once that I know it's googlified. SearchYC works! with lots of criteria. imho, this would reduce many of'django vs rails' kind of questions, that have been discussed in the past.