Hate to be a buzz kill but you can be poly and cheat. . . and then the next question is: what is considered sex?

It's a case of damned if you do, damned if you don't. I personally would be my first choice to not get involved with someone's relationship. That is their business not mine. If I knew my friend was going to get hurt, I'd feel bad and might send subtle Hints their way that something is up, but out right telling them would most likely not happen. Most likely doesn't mean never.

It's something that I take as one case at a time, I have no real rules of thumb except to not get involved where I'm not needed/wanted.

~RK~