Sometimes, children don't notice their parents noticing. And that's great for kids. They're safe, but don't know they are, so feel powerful.

If the children notice this they may assume that you either condone, accept, bear or ignore it. None of these has positive effects

Why not? It depends on what your goals are.

I think it's pretty useful for kids to learn that the explicit rules aren't the true rules. And that authority does turn a blind eye sometimes.