Keywords are inclusive, so the more keywords you put in, the less lines you'll find.
You can specifically ask for a keyword to not exist by prefixing it with !.
For example, searching for "mouse !cheese milk" would find lines that contain both mouse and milk but not cheese.

[050413 04:25] 389f9, Valor: Anarchs shmanarchs I say!

[050413 04:37] d36de, Peanut: ....someone posted recently...strange

[050413 04:41] d36de, Peanut: This room is rather humorous these days, people come here to 'tag' it as a vague memory of something long gone.

[050413 06:06] 89f89, Valor: Wow, you should like... write cultural criticism cause you're so smart

[050414 04:36] d36de, Peanut: Valor being a smart ass? Wow, I'd never of thought!