I did a negotiation yesterday with Sal which was with a character that gave me a bane eariler in the run, and it's one of those times that the game lets you defeat people that hate you to get rid of the bane with no further negative things on you. (First with a negotation in which no rewards are earned expect for experience cards on cards and their upgrades, but you are rewarded for the battle.)
Anyway, during the negotiation part of it, an argument showed up on the AI's end that said "When this argument is defeated, gain an X Matte passive argument, with X equal to the remaining stacks of this item. If you win the argument, gain X Matte as a bonus." I was able to defeat that argument in which I would have gain 7 Matte after the negotiation, and I did win it, but the game did not credit the 7 Matte I was owned. It also did not show up in the battle rewards, either.
In addition, after that "bane" event, the game treated the next quest I would have done as a failure since this person was defeated, but I haven't ever accepted the quest yet. (For this example, the quest was G is having trouble paying off a debt, and wants me to talk to P to get better terms for it. The reward would have been 110 shells, and being able to remove a card from either of their decks. However, after defeating M (who wasn't part of the quest) and before accepting the quest, the game treated it as a failure, and I didn't get any rewards. This was before I accepted it.)
Unfortunately, I don't have any screenshots to share of this, and I only explain it in words.
Find an negotiation in which a "bane" negotiation pops up with a Matte argument reward on your opponent's side, and win after defeating it. Then, just to complete a quest after that.