Who keeps down voting the people who are making their case in this thread? They aren't being rude or unkind, they are simply stating their experience.
Luna, you are very, very lucky if you don't experience report warnings in games. It doesn't happen as often to me any more, but I have seen it over and over again on the tribunal. And yes, I have experienced it. People who want to report because some one is having a bad game.
Vynliean, Luna makes a good point when they say "what would that report sound like?" If you have not been rude or crass, you will not be punished. Feel free to report them afterwords if they have been negative the entire game.
Also, don't forget the mute button is there for a reason. It has helped me get through games many times.
To sum up, report warnings are frustrating, but as long as you stay classy there is nothing to worry about. Try not to let toxic players "poison" you. Obviously they have a very poor understanding of the tribunal anyways.