All of the above? Shadowheart's lack of initiative to actively pursue relationships or attachments is honestly probably one more bullet point for why she's so important to the Shar cult she's in. She expresses herself quite openly, but it seems consistent that someone else has to take the first step. As you said, Karlach can't. For all his Act 3 design problems Halsin likely would have if he were an Origin, and his code certainly has him acting the role of pest interjecting himself when he thinks he has a shot to shoot.
Karlach still tries with the PC, why couldn't she with Shadowheart? She just can't sleep around, but you can kiss Karlach in act 1 as well. Shadowheart doesn't sleep with anyone, including PC. She would've if she were taught in an environment where casual sex was encouraged. And judging by her relationship with Halsin in act 2, she would've declined him. They're not exactly friends.
Originally Posted by Auric
In terms of what's stated, there's that pair of rings that have a whole story about a Justiciar who built someone up into loving her completely, enough to accept a ring from her. It was to take advantage of him so he would unwittingly tank damage to help her survive, but the game establishes the precedent of this particular brand of distraction decently enough imo. We don't get basically any exposition about the specifics but between that, Shadowheart's comment, and who the current figurehead of the cult in the game happens to be, it all makes sense to me. In my estimation Shadowheart's personal lack of initiative to get some casual fun in the woods (and the way she mentions that if you pitch it to her implies a little past personal experience) is just one more reason she was groomed into such a central role. The player character has to put in a fair amount more effort into assuring her of their sincere interest than pretty much anyone else because she does kind of resist in hopes of being elevated to a position that WILL demand more devotion to Shar, but that's not being demanded of her yet at game start and the more she likes you the less she's willing to pass up the chance while she's able to take it. I think it pretty clear she could easily have ended up liking Karlach enough for that too, and maybe would have even given Gale a chance for at least a dalliance if he ever made a move.
The rings imply seduction. Seduction, casual sex and relationship are three different things. Seduction is using sex as a purposeful tool and Shar does approve of that. Other than that I don't see where you disagree that it makes no sense that it was supposedly encouraged. She can't be both embarrassed by being attracted to someone and avoid any initiative for casual sex, but at the same time claim it was encouraged and she has stories to tell about her doing exactly that. That's the very definition of contraction.
Originally Posted by Auric
See this I disagree on mostly because as you mention, the Origins were arbitrarily left out of the poly dynamic. Rather than it being out of character for Shadowheart or anyone else for that matter, I see it as a design shortcoming that you can't include anyone else even for example when Karlach fully volunteers herself to be included. Larian decided not to make the effort to fully follow through on that dynamic for reasons only they know, but even if we did know them I bet they'd be equally as baffling as making the endings people expected and deciding not to use them, or rushing the game out a month early.
Certainly she expects faithfulness. And part of that is the expectation that you don't pull shit behind her back which is exactly why she still chastises you about Mizora even while being quite forgiving of it.
-edit- sorry some of this sounds like it's just repeating things you already said in the last few posts, I had to afk in the middle of writing this so I didn't see them until after.
Astarion also accepts poly with Halsin for absolutely no reason just to fit Halsin's late addition. Just like Shadowheart, it makes literally no sense for him to be okay with it. Just like Shadowheart, he's okay with Mizora, which also doesn't make sense. It all leads to one simple explanation: Halsin can't be poly/open if he's the only companion that is, and since he was a late addition romance they retconned Shadowheart and Astarion to illogically work with it.
And like you said, for some reason they aren't allowed to be poly together. Which just gives more credibility to the notion that the only reason these inconsistencies exist are because of Halsin's late addition, which in fact does make them exactly that: inconsistencies.
