Originally Posted by Anska
I am not too fond of Halsin the companion (he is fine as an NPC) but his behaviour has been changed with the latest patch, for example the "glad to be had" line upon recruiting him after Thaniel's quest has been replaced with something less flirty. He also does not proposition you if your approval is neutral, which it now automatically is if you don't take him along for Thaniel's quest. So all in all, he has become quite harmless if you just let him chill in camp and just chat about ducks with him.
Did you try that mod that reveals what flags get triggered? I remember seeing almost all his dialogue options being considered as flirting at one point.