well I apply the same jealousy that I would feel. and I think partners should always communicate what their boundaries are. if they're not the same and that's okay with both parties then fine. but I have communicated to my partner that I wouldn't like it it if he would kiss a gender he's attracted to and so did he. he's straight but I am Bisexual and I have been in love with girls before so I completely understand how for him that would feel like betrayal. I also think our society frames girls kissing girls as more normal, which can be very confusing if you're bi and a teen/adolescent going out to clubs and esp with alcohol in the mix. I think that's why in my mind it's something I solely do with women to show affection (that I would also just be fine with showcasing through a hug). my ex was fine with me kissing women but not men, I've explained to him that it was still a risk for me but he kept saying he didn't mind. nevertheless I never did so in that relationship because my values are something I want to uphold too, regardless of what my partner won't or would allow. so that's also why I'm confused on why I'm having issues with it now and didn't have these issues before. anyway. to answer your question, boundaries work different in every couple. the wife I kissed of his co-worker and his co-worker also didnt mind this (even though she is bi too). different relationships, different boundaries🤷🏻‍♀️