(neutral btw, was that negative changed to neutral?).
no, it is more likely that neutral will change to negative than vice versa.
In this I do not agree with you at all. You are basically telling two criminals to hide the evidence of the crime, so to speak.
It is rather inappropriate to compare plagiarists with criminals. Let's put them in jail.
And they did not hide it, but corrected it. These are different moments. If the forum directed all its efforts to punish plagiarists, then global moderators would ban everyone based on evidence from archives or quotes. But the reason for the ban is current plagiarism, here and now.
If you correct plagiarism after detection, but before processing the report, you are no longer a plagiarist, the forum will not punish you. And depending on what is meant by repeated violation. If all the plagiarism is detected at an earlier time, this is one moment. The user could not maliciously post such messages. And if plagiarism happened constantly, in different years of activity and under different ranks, then this is already another moment.
What's your vision? Stop the spread of plagiarism by removing it and correcting the user who made a mistake so that he understands that it is not worth doing this, or in any case, make sure that he is banned forever, despite the fact that he is ready to correct himself and continue to be a part of the forum? I choose the first option.