You keep using the word relationship, and I think this nails down the problem.

Halsin himself says it is not a relationship. It comes and it goes, it's fluid and it happens whenever you feel like it or the other person happens to be around. It is a person you care about and have some affection for, but not someone you build a relationship or a future with.

This has a name: Friends with Benefits

As polygamy goes, this is what the connection to Halsin is.

You had tons of players asking for a romance/relationship with him. And that can take many forms. But this isn't a relationship and that is part of the issue with it.

It's momentary amusement and passion, that at the start is given the wrapping of a deep and lasting connection, where Halsin eludes to only involving himself in things he DEDICATES himself to.

And what does Halsin say? "I will not ask you to dedicate yourself to me".

Another thing is; Why do you add a character on player feedback that have gotten so attached to a character that they have pined for him for three years, and then make it fleeting?

I see your point, but it rather seems like you are missing the point as to why people are dissatisfied and making it about representation rather than what it actually is: Poor implementation of requested player feedback