What Michieltjuhh said, basically sums what Halsin is all about.
Halsin adds nothing besides saving Thaniel (IDK if you can save him by another means). Everything else he says you can figure out yourselves. Anyway... If you deny his proposal of becoming a lover, apparently he game will keep pushing you (forcing you) to love him.
1. He gets in your camp even if you don't want to
2. If you reject him, that means you don't like him... no matter if you are taking a mono or poly path... If you are gay, it doesn't mean that you like every man on the planet. Then, only because I want to go poly in the game, that doesn't imply I want Halsin to be my second lover.
3. If you already reject him, why would he stick his nose and ask for a fivesome... No Halsin, no is no... I don't like you I want the twins and SH, not you... (and then the disapproval, LMAO)
4. If I'm going mono, why showing that nasty banter after the swimming scene? Even more, if I'm just talking to the twins, why would she say "There's an idea. If you're comfortable sharing... so am I"? What happens to all the "you and only you"? Before the player's response
Tons of inconsistencies... Is the game reacting to the player's choices, or the game forcing you to choose a certain path for the shake of someone's dirty fetish?
Are you telling me to go poly even if I don't want to? Specifically with Halsin? Are you saying I need to do the fivesome if I don't want a disapproval? Wow thanks for respecting my choices and narrowing my options.
Then, what? I need to kill him? Or her? Should I go the dark path? I need SH to kill the nightsong? I need to leave Halsin in the camp even if I like him as companion (for the fights I mean)? Oh wow, In other words: you need to react according to the game, because all roads lead to Rome. Let's throw your role play to the trashcan.