So, what's the deal? Do you trust your partner? If not, why not? In my opinion, there's never a justification for going through your partner's stuff. Asking for a friend, obv.
I think that the act of snooping creates an adversarial, suspicious atmosphere. I think that's the main reason it's a hardline rule of partnership: don't snoop. Even if I suspected my partner of cheating, I would not want to snoop. I hate games. If I didn't feel I could trust my person, I would break up with him. I don't need photos or liaisons to prove it. I know things in my own heart. But if I knew they were stepping out on me, I wouldn't want to dial up pain by poring over their words.
So, the guy got up in the middle of the night, went through my phone, misread the date on a friendly text with a guy I had gone on a couple dates with a millenium ago, a text which actually said, "No, I've just started seeing someone," and woke me up ballistic. Ballistic. Having misread, after having snooped. I am tortured right now because I feel that this is dealbreaker behavior, but he's also been hurt tons in the past so maybe I'm supposed to be forgiving. I feel terrible. My real question is: what does snooping rate on the scale of No You Didn't; Fuck You?