Reddit only allowed 6 choices, unfortunately, and the actual Baldurs Gate 3 subreddit doesn't allow polls. Halsin is the most underdeveloped out of all the companions that have years of writing backing them. So obviously people will like him the least, there's not much there to like in comparison to the origin characters.
Doesn't help that his behavior offends some people, with the alluded beastiality and buggy forwardness that makes him look very strange. The game just kinda assumes you want to bang him.
As for His preference for more than one partner, it isn't Polyamory as advertised, it's just an optional open relationship. He even ditches you at the end, so it's more like an optional one-time affair with consent lol
Mizora is my favorite character in the game.
What exactly do you like about Mizora, be specific