Glad to have found a thread about him - there is also discussion on Tumblr about the same topic.

I was hoping for a monogamous option with him too but seeing that wood elves tend to be poly I can live with him being poly. But as already beautifully said in the OPs post, it is about how his romance is written.

I really don't want to sound ungrateful, it is awesome that they added Halsin as romance to the game. It just could have been amazing for everyone - for those who just want to bed him and for those who were waiting and hoping for him as romance partner, not just lust object.

Even wood elves marry from what I have read. Especially with races that are not very long lived but also with other elves, but seeing that elves live a long time (high level druids especially with the timeless body feat, also I am not sure if this can be willingly controlled by them so that they can but not have to live longer) it is kind of understandable that they are hesistant to commit to a life long marriage. Also even if married, it is not like you are chained to your partner, I think they could break up later too as people might change or fall out of love so I don't really get this let's not marry, I don't know if I will still love you 500 years from now...

Marriage option with Halsin would have been amazing but even without it you can write characters as being in a serious and meaningful loving relationship with another.

But with Halsin you don't even know where you stand. Sometimes it sounds like he is really in love with Tav (at least at the moment) with knots in his stomach, his heart stirring, his romantic lines... but then again it is like he doesn't want to admit it is a romantic relationship at all, he doesn't even want to call it a relationship. Like always shying away from admitting that it is really something deeper.

I mean I guess who just wants to have sex with him no strings attached will be very happy indeed. But for those who hoped for more it is very disappointing. You can't even go with him in the end - not like Tav really has other things do to, why can't we tell him we would like to accompany him and helping him starting a new settlement, helping the people and raising the children? And then he comes again with the romantic lines that he will think about you...

It is like he had his fun with Tav, he is happy if you visit him to have temporary fun again but please nothing serious or longer lasting. Like he only wants some one-night stands or short timed sex relationship and nothing more. For a man with 350 years of experience and his many lovers that he already had you might think he would now start to calm down and look for something stable. But then you have the Dryad scene and him talking like he is really in love with Tav, that he only wants Tav - that just doesn't really fit, it is so inconsistent. Or maybe I see it wrong and it is just Halsins issue that he has trouble forming stable relationships despite being in love? It just doesn't feel like you can have a serious love relationship with him.

Or why do you have to do a foursome with him and the drows to find out, that he was chained 3 years in the underdark to a bed chamber? The scene itself (what you read) is also written to be funny and then you get this dialog afterwards... if you do not do the foursome you will never find out that about him (and that while people who like him surely want to know as much as possible about him) and if you do it doesn't feel good to have this traumatic experience after this just funny sex scene (also it doesn't come across like this when he speaks about it, more like it was a adventure of some sort). I mean, I just wish there had been a different approach to that. And having an option to decline the sex telling Halsin that you prefer to be just with him.