I do not believe that common courtesy should have anything to do with properly positioning oneself, scoring points, earning a good reputation, or anything else remotely associated with a "zero-sum game".

We should be courteous for one reason only: because it's the right thing to do.

The older I get, the more I realize how unimportant most details are and how critical some of the big issues are. I don't think anyone said it better that Hillel: "That which is hateful to you, do not do to your fellow. That is the whole Torah; the rest is the explanation; go and learn."