People who never learned non-conflict intimacy can grow up into people who constantly make sharp jokes and tease rudely. Sometimes they're actually mean-spirited but I think most of the time they don't know how to feel connected any other way. I think this is also part of the reason that people fall in love with mean, selfish people: they are a huge source of conflict, and if that is the only way you know to be intimate, a relationship without conflict would be one without intimacy as well, so it seems 'boring.' Really it's that the skills for non-conflict intimacy are so much more work and take more risk because you have to learn who you really are, and then share that, which means a potential blow doesn't glance off your shell, but hits home.
There's different varieties of conflict intimacy of course- the simple bratty kind that usually isn't consensual and can't mature, the unresolved kind (with anyone whom you can't or won't work it out with) that doesn't mature, and then the constructive kind, which matures through resolution into a deeper understanding of the other person. That last kind is obviously my favorite. Recently there was a conflict between Roger and Heather, and another between Kei-Won-Tia and Zawn, and all the people involved used it constructively and because they shared the process with me, not only are they (potentially) closer, I feel closer to each of them through empathizing with their feelings and learning about them through their reactions.
Constructive conflict intimacy takes a lot of energy though; if there isn't enough non-conflict intimacy then you'll get worn out and eventually not have enough energy to engage, and then your conflicts will be unresolved and your intimacy will stop being so nourishing. This happened with me and Kylei when we were both depressed and being crap at self-care, and neither of us realized it was happening because we had always had a lot of conflict, but we had also always had a lot of non-conflict intimacy through mindful touch and silliness/play. When our non-conflict intimacy stopped happening, we still felt intimate but it didn't feel good, and we didn't really understand why. Eventually we got to a point where we had endless unresolved conflict and even though we were still very much in love, it was terribly damaging for us to be together. Since then I've learned that conflict intimacy sometimes needs to be avoided for a little while and other intimacy needs to be used. So if Topaz and I are having lots of hard conversations, usually we'll have a little down time with casual cuddles while watching a show and then we'll have focused mindful touch while silent. I always want to get all the hard stuff over with so it can be very hard for me to put a conflict on pause but if I didn't learn to do that I'd be making energy deficits that were much harder to fill back up.