I don't think they are at all. I believe everything, from getting a "stuck" thread in "Ask HN" and "Show HN" all depend on votes. If people aren't voting, it means that whatever you posted is just "average" and not something that is unique or stands out.<p>Users can "flag" your post and then it seems to drops faster out of sight and out of mind, and it loses it ability to acquire any comments.<p>Upvoting tends to bring your post up top and I've heard of posts going "viral for 24 hours on the front page of HN" which means it must all have to do with voting and comments. I haven't seen too many people claim anymore than 24 hours though. It makes sense, specifically to gain attraction from users, and of course, the more comments there are on a post, the higher it is likely to be ranked in search engines.<p>As far as the 24 hour period, that too makes sense, as they probably don't want the same thing being up top for too many days, weeks or months at a time, which encourages new materials all the time.