What's the point in 'going steady' then if the game kind of considers you to be in a relationship when you're at the 'romantic interest' stage? Weird.
I've cheated loads in the game, I've played out all kinds of fantasies, but that's what the game's for. There's a great big fat line between the game and real life. I even had a sim version of me and my partner, and had my partner go off with someone else. I didn't really intend for it to happen, but she was at their house and they were getting on really well so I thought what the heck.
As for real life, yeah it all varies culturally quite a bit. And even within the same culture age and a bunch of other things probably come into it. I've always flirted with my friends but it doesn't mean anything, I also flirt with random people sometimes just to brighten mine/their day. Again, only in certain situations where it won't be taken the wrong way. My ex was Finnish and it's like you just have to smile at someone and it's taken the wrong way with Finns, I got into so much trouble there.
I think people's line of acceptability is in slightly different places. They key is to find a partner whose line is in the same place, and with who you agree with what it means to cross that line.
I wish the Sims had an option for open or polyamorous relationships, it would be way more fun.
[edited for language - Ausette]