Saying “I don’t know” is also very important for devops people, but for slightly different reasons; we’re likely to have a little bit of knowledge about everything, and it’s import for us to be explicit about where our expertise dries up.

I say a lot of things in the form “I’m a little out of my depth in this subject, but my best understanding is that the behavior should be such-and-such; does that sound right to you?”