Random discount => tip situation?

[GuyOnTilt]

If I noticed something wrong and thought it was a mistake I would say something about it. But I don't really see anything wrong with you doing what you did. At more restaurant'ish restaurants, I very rarely look at the check before just sliding my card halfway inside, but servers give free stuff often enough on purpose that I don't think the possibility of something left off being a mistake would cross my mind even if I did notice it. Maybe if it's something absurd and the server never mentioned anything or seemed like they especially liked our table I guess. But yeah, it's commonplace enough that I would just tip more if I noticed.

GoT