I think the concern is still valid, it’s just one of those problems where some solutions could have the potential to do more harm than the problem itself.
Let’s say there was a “report abuse” button. If you first performed a check on the user submitting the claim (i.e. have they submitted more than one of these claims in the past week or two, if so – reduced the weight of their claim) and then checked against the accused (i.e. has this person received multiple claims against them in recent history, was it for the same behavior). I imagine they could establish some system whereby users could get temporary tags based on what they were doing (e.g. intentional friendly fire, verbal abuse, etc). This would at least give other players a warning.
I don’t know that I’ve ever experienced a situation where I knew I was matched with the same jerk twice. I can appreciate a personal desire to blacklist players; there was a Quality of Life mod in V1 that allowed you to do that – and it did give a minor feeling of vindication.
On the total flip side, I’ve had matches where I was trying to get experience with a low level character, and my team was taking more grims than they could handle, and I have certainly tossed one in those instances. I have a friend who actively dislikes the time wasted getting jumping puzzle books, so he refuses to get tomes some times. In these instances, sometimes the various players are just playing “different” but still valid games. Part of me thinks that allowing players to add optional tags to a quick play (e.g. full book) might allow players to voluntarily sort themselves better – avoiding this sort of issue.