Awww, you're taking me back in time ain't ya?
That pop up you are talking about is not a warning that you are being toxic. If I guessed what you are talking about correctly, this should be in the time of the Tribunal. That pop up simply tell you that you have been reported in the majority of your games. It doesn't mean those are valid report or you are being toxic, just that you are reported too much. Now you can infer that maybe you are heading down the wrong path before people don't just report everyone for no reason. Still.....
Now we go back to the present. With the IFS capable of judging a report within minutes as oppose to the Tribunal taking days/weeks/months, there is simply no need for such a pop-up because the IFS can judge whether a report is valid or not quickly. A pop up that tell you you've been reported too much doesn't seem logical.
Perhaps you leaned toward some kind of toxic progress bar that when you get close, you get a pop up warning. It's all nice and good, but true toxic people can use it to gauge their toxicity and how much they can push the system. If they get the pop up, they lay low for a bit and then be toxic again. If they don't get the pop up, then toxicity awayyyy.