I literally got reported for doing nothing wrong

In my last game as Nautilus support, my game was going well. Yes, I admit, I have been toxic before, but don't hate on me, I am working on it. This game, I did absolutely nothing wrong. Our game went slow, but I never cussed, never said anything bad, only good talk with the team. I commented on how slow the game was going as it was past 15 min or so and the game was tied at 1-1, then later when Nocturne was ganking me and Tristana, our jg Kha'Zix comes in and helps, and I get him two kills while Tristana gets away with like 20 health (our adc). I commented how we couldn't get her the kills but at least we saved her from dying as she was being focused and I got my jungler two kills. Then the enemy surrendered and at the end screen, I get a warning for negative attitude. Like what the heck?

Don't just report people for literally no reason. Why is there any reason for you to do that at all? Play the game properly please. Thank you.