The problem is "Internet Memes" are basically opinion pieces and opinion pieces, by their nature, inspire an emotional response from the reader. That makes the reader more likely to vote and/or comment on an opinion piece. As opposed to what you'd call the "Content Posts" like...for example...a great tutorial.

I hate to be a back seat webmaster but the time might be coming where HN has to split the Internet Memes and the Content Posts just to keep the later from being overrun completely (which is basically where we are now)