Thank you for posting this! I felt this way for a LONG time. Larian said companions would be "player sexual" and NOT "player and Halsin, and everyone else sexual". Why make Shadowheart LUST after other companions when you're in a committed relationship?? I get having a Poly option for people that want it - that's fine. But it should be DRIVEN by the Player, not written in the subtext of the whole Romance.
Basically, it just sucks the way they currently wrote it. Shadowheart's hidden (or not so hidden thanks to the internet) fetish really ruins her character.
It's like they decided they couldn't keep the Shadowheart romance the satisfying "slow-burn romance" they advertised. It was so perfect the way it was - a long period of building trust, learning about her, she slowly opens up more and more, and only after 80-100 hours of gameplay do you have your big moment with her. It is so powerfully intimate. It means something because she is sharing herself with you when she was so "hard to get" in Acts 1-2. It's a scene that rewards the player for their dedication and diligence - turning down other "quick sex" options that many of the others offer - to be with HER. "No, I want you - Shadowheart - because I know what we have is special. And you agree!"
Shadowheart talks about how much you mean to her. How special your relationship is.... oh but she'll totally have sex with Halsin and has been "DREAMING" about it. Like, seriously - WTF?? And for a guy that preaches about Consent and Honest conversation, Halsin is quick to try and worm his way into your relationship. Turning him down is of no avail - he and Shadowheart are just itching to have sex with each other. They flirt with each other - even encroaching on your swimming moment with Shadowheart with their dialogue. If you talk to the drow prostitutes, even just out of curiosity - Halsin and Shadowheart gang up on you and BEG you to let them have a 5-some. Say "no" and you're SMACKED with Disapproval from BOTH of them. If you do agree, you basically enter a Porno where you're a cuck sitting in a chair while your "friend" rails your girlfriend. Talk about a bait and switch!!
And you have really no say in any of this, again, because turning Halsin down does NOT change his behavior. And you can't establish boundaries with Shadowheart in any way. Your options are to ignore it and pretend it doesn't exist or be met with a companion that is so eager to have sex with others that it is offputting in the extreme. A character, mind, that just a little bit ago wanted to settle down with you and said that you're her True Love.
So yeah, I really wish they would make these optional things MORE optional. As in, if I don't want a poly relationship - DONT FORCE ONE ON ME by making my otherwise excellent companion a horndong who wants to have sex with anything that moves. At least let me establish boundaries with her. Let me tell her that "No, dear - we're not opening our relationship" and Shadowheart (who says she loves you) should stand by you in that decision. And then the characters should HONOR this CHOICE. This choice should mean that - Halsin shouldn't be flirting with her, Shadowheart shouldn't be looking to hook up with prostitutes or lusting after Mount Halsin, and Cheating on her should be met with disgust and disdain and have severe consequences.