Have had it happen a few times, only happened when using their official client too. Appeal went through nearly instant every time with I think you made a mistake. They were all accepted and the accounts were unbanned.
I've ran 80 accounts on the same ip at the same time doing the same thing, only 8 got banned after 20 hours. I think running 2 accounts on the same IP is fine.
If you have any actual proof of the user scamming that doesn't completely rely on trust of a person then make a dispute. Other wise enough, go your separate ways, this goes for you both.
Feed back removed as it's irrelevant quarrel.