I couldn't agree with you more. And with that said. Should a Christian be going about idly flirting with everyone, or only with a particular person they're interested in?
If you and I are friends but I have absolutely no interest in you, can I still flirt with you, because it can be a "fun" activity? Is it OK to flirt with people simply as a joke? This is what I have an issue with. Also, would you be OK if your spouse flirted with their friends or coworkers? Would you see it as a joke or harmless fun?
Flirting when you are married with other people than your spouse is a huge NO! NO!!!!!
Where to draw the line is a difficult question. As a teacher I use to make eye contact, smile, remind the student about his or her strengths, affirming their value. That is proffessional leadership. If I did the same in a bar (which I am too shy of doing) it could be considered flirting. For me, though, showing genuine interest in people is a way of living (except in making contact to strange men in a bar). It is not a way of flirting. My mother once said I flirt, though. For me, it is nothing sexual in it, but a way of creating contact, whether it is with a waiter or a student.
To go beyond that is a mystery to me. What is flirting, if not showing an interest in someone? And how to interpret those signs of interest. Like today a new co worker introduced himself to me and opened the door to me. He was really nice, remembered me from the previous day and very easy to talk with. I wouldn't say he was flirting, but maybe he was....