There's no effort being made here to defend certain actions. The only effort being made here on my part is to question how much work has to go into a character before game players stop reducing characters to things like "drug dealing scum" as one individual so eloquently phrased it. Being judgmental of fictional characters in a visual novel seems a bridge further than one should be willing to go. It's a game. It's not reality. Quinn could turn out to be everything the players who dislike her character think she is but events in the most recent episode say otherwise. They say Quinn is going to rise above her life circumstances and become something more than the basket into which she is being placed. The MC has the same story in some ways. He is also trying to rise above his lot in life. They like each other because they have things in common. They are both trying to fit into a world where they feel out of place. The MC is just better at it. The MC is socially awkward. Quinn is socially inept.
But my main objection to Quinn isn't that she sells drugs (or runs a prostitution ring), it's that Quinn enjoys making others suffer. I dislike that trait intensely, and I see very little sign it's going to change anytime soon - if indeed it will ever change. Nothing we've seen in the last two episodes shows Quinn struggling with this trait; if anything her scenes with Maya show her reveling in it.
Furthermore, unlike the flaws of other characters (such as Jill's naivety-bordering-on-stupidity or Maya's passivity), I see no
direct connection between Quinn's upbringing and her sadism. Rox is dangerously unstable and Quinn's presumed mother is a burned out wreck, but neither is seen tormenting other people for the lulz. Similarly, Buddy does not show any glee at Quinn's misfortune and even seems interested in what might be going wrong for her (though I admit it's possible his motivation was not her wellbeing).
So where did Quinn's mean streak come from? It's certainly
plausible it could have sprung from some aspect of her backstory, but nothing we've seen onscreen actually shows the link. For now it's just informed speculation.
And hence my question: is it really fair to blame Quinn's flaws on a bad childhood when a) it's difficult to be certain exactly how bad Quinn's childhood was in comparison to other characters' and b) it's unclear exactly how much her childhood had to do with shaping the worst aspects of Quinn's personality?