I kinda agree with you partly but, just playing devil's advocate here, one could make the exact opposite argument in that just because you'd like to keep it serious doesn't mean everyone else feels the same way.
Well, I come to hacker news to read news and to learn, not really for laughs. Sure a bit of comic relief here and there is okay, but god when the site gets covered in junk links (which rarely happens but I've seen a few bad days) -- it's beating the purpose of the site.
