Yeah his dialogue needs to be cleaned up and properly flagged.

This playthrough during the tiefling party I literally only said to him to 'take his own advice and mingle with the others', just a perfectly normal civil response that ended the dialogue immediately. The next morning both him and my character acted as if she came onto him super hard all flirtatious while completely wasted. By ACT III he is madly in love with me, impossible to have as just a comrade in arms.

Even if he is meant to be so easily enticed by a simple civil interaction; I personally don't mind it but it definitely cheapens his character (and our own) for not having any boundaries. Because his purpose as an ally/friend/comrade is to cleanse the shadow curse and help against the Absolute, so him so openly expressing his desires towards us from the very get go and all the way to ACT III seriously destroys the image of a wise war veteran that fought in the battle of Moonrise Towers and survived its horrors after losing so many friends to the curse.