I agree with you overall, but the real problem is that the Affinity system sucks. If we grant DPC's premise that the Major Decisions (and
only the Major Decisions) are the key moments that form the basis of the MC's overall personality, Jill rejecting a DIK makes a lot more sense. It doesn't matter if Jill knows about each decision directly, because an MC who made those Decisions will be acting all the time like someone Jill wouldn't want to date. That's the theory, at least.
Consider the Decisions for a moment. By the time Jill makes her fateful decision near the end of Episode 7, we've had 13 Major Decisions, and DIK Affinity requires making at least 8 DIK choices. How many of those decisions could only be made by the sort of person Jill strongly objects to?
- Beat Up Troy - This is probably a Weak objection. The MC doesn't realize Troy was being bullied and lashes out because his guitar was stolen and Troy had been a relentless jerk to him. So while Jill doesn't like violence and would disapprove of her actions, I think she'd see this incident as more of a teachable moment than a real red flag.
- Join Quinn's Restaurant - Strong objection. This one's pretty obvious. Beyond the simple jealousy factor, buy sex from girls requires a view of the world Jill would not accept.
- Don't Forgive Steve - No objection. Sure, Jill would probably prefer an MC who always comforts a sobbing individual, but that would be going over and above the call of duty. Steve is another character that's been a relentless jerk to the MC, so the fact that he doesn't care when something bad happens to Steve is not a sign the MC is particularly vindictive. If the MC forgiving people was a regular part of the Affinity system I might buy it. But as a random one off? No.
- Fight the Jock Trio - Weak objection. Again, Jill dislikes violence, and if you read between the lines, this is supposed to be a case where the MC fights unnecessarily. So in theory Jill wouldn't approve, even if it hardly feels like a deal breaker. Of course, in practice the logic of this being an 'unprovoked' fight is laughable which ruins the notion Jill would object, but I'm trying to give the devil his due here. We'll just pretend this makes sense and move on.
- Party at the Pink Rose - Weak objection. Jill would definitely prefer a guy who has no interest in the Pink Rose, so this is at least a Weak objection. It could arguably even be a Strong objection, but that would really depend on the actions taken by the MC subsequently. Getting a lap dance seems like something that would make Jill very uncomfortable, but that she wouldn't feel is beyond the pale if done in moderation (before you're a couple, at any rate). Fingering Lily's ass WOULD be huge problem, but that option is actually governed by a different morality system, making a complete mess of the whole idea Affinity represents the MC's attitude. Let's call this a Weak objection and move on.
- Start an Affair With Jade - Strong objection. Not much wiggle room here. Dating multiple girls is one thing. Deliberately encouraging a married professor (who also happens to be Tybalt's mom) is on a different planet. No way Jill overlooks this sort of thing.
- Do Drugs with Quinn - Weak objection*. Jill is clearly a fan of sobriety and moderation, so I think it's easy to say she wouldn't like the idea of the MC smoking weed. But given that she tolerates his plot-mandated drunkenness without issue, I can't see this being a significant problem; it's not like weed has become a major vice for the MC since then. I think the much bigger objection for Jill would be if he fucked Quinn, but that's a separate decisions that inexplicably has no impact on the MC's personality. NOTE: The one caveat here is that if Lana's death had something to do with drugs, this could suddenly become a much bigger stumbling block for Jill. Since we don't know that, however, I'm leaving this as Weak for now.
- Fight Caleb - Strong objection. YMMV, but I think it's the only fight in the game that the MC really does have an easy way out of. Yes, his pride might be hurt, but Jill is exactly the sort of girl who would expect the MC to turn the other cheek. As far as Major Decisions being windows into the MCs soul, this is probably the best example. I can easily believe an MC who'd step up to fight Caleb really would constantly project an aura of bravado that would discourage Jill.
- Punch Tybalt - Strong objection. Granted, few people deserve a boot to the head more than Tybalt, but at the end of the day he is precisely zero threat. Punching him is like slugging an obnoxious 10 year old. Compounding the issue, Jill apparently believes the MC was doing something shady in the first place, AND this is the only Major Decision that is brought to Jill's attention directly. So yeah, this is a major strike against the MC. Jill would accept this as a mistake by the MC if it's the exception, but not if it's the rule - which is precisely what the Affinity system is supposed to represent.
- Fight Tommy - Weak objection at best. Again, Jill dislikes violence and would want the MC to diffuse the situation if possible. But given that the MC was doing absolutely nothing wrong when Tommy sucker-punched him, it's a bit of a second guess to think he could have instantly diffused the situation just by asking why Tommy slugged him. If we squint really hard, we can see this is an indication that a DIK MC has more of a hair trigger than a CHICK one, but even then we're bending over backwards to justify a pretty mild objection from Jill.
- Take Tommy's Fake ID - No objection. Seriously, why would Jill care? We're explicitly told that even Jill herself indulged in a little illicit alcohol use thanks to Bianca.
- Work at the Pink Rose - Weak objection. Much like the original PR decision, this is basically an indication the MC likes staring at naked ladies. Jill isn't going to like that and it's easy to see how this attitude would be readily apparent in the MC's everyday actions. But simply looking at boobs, especially when the DIKs do need the money, still feels like too minor a transgression to merit a Strong objection... especially when keeping the VIP card (a MUCH more illustrative example) has no impact on the MC's personality.
- Make Jocks Leave the HOT Party - Weak objection. The MC is deliberately stoking a grudge rather than letting bygones be bygones, and we know Jill would prefer the latter. But the MC is also deliberately moderating his actions to avoid causing a fuss, and for the most part his tactics aren't even particularly bad. Pushing Dawe into the pool is the only real bit of bullying here. I think Jill keep trying to eliminate that last step into outright bullying, but could accept an MC capable of doing the rest.
So there we go, only 2 DIK Major Decisions feel like non-issues for Jill. The rest are at least marginally problematic, and the MC needs to select 8 of them. So I think you could make a decent argument that Jill rejecting a DIK MC makes sense... if we're only looking at the rejection case. The problem is that Jill will accept an MC who's taken 7 DIK actions, and as we've seen, not all of the actions are equal.
Let's test the system. MC1 Beats Up Troy, Doesn't Forgive Steve, Fights the Trio, Does Drugs With Quinn, Fights Tommy, Accepts the Fake ID, Works at the Pink Rose, and Makes the Jocks Leave the Party. MC2 joins Quinn's Restaurant, Fights the Trio, Starts an Affair With Jade, Fights Caleb, and Punches Tybalt. Are we really supposed to believe MC2 would somehow come across as more wholesome to Jill than MC1? Yet MC2 is supposedly good to go because he's a CHICK - as long as he ditches Sage, of course. Helping sick friends is going too far!
So yeah, even if we give it the benefit of the doubt, the Affinity system just isn't capable of doing what DPC needs it to do. The Major Decisions aren't major enough to truly define the MC.