in my idea you should put a negative feedback for now and after proof ownership by sign message you can remove feedback
Then your idea is wrong because it doesn't work like this.
It's like if I say you should go to prison and only then it's up to you to prove you're innocent.
First, you prove that he is guilty
and THEN you take action
Your accusations are based on almost nothing. Listening to people, we should put negative feedback just because they say hello
Additionally, since you judge his post history and say it has changed since he came back... he posted only 4 posts since. Very insignificant to give conclusions