I wish I could find the original source on this, but I remember reading a tweet or blog that I thought had a really good metaphor for this kind of "male friend ribbing."

The metaphor went something like this: men making fun of each other are actuall y showing that they understand their friends deeply, because they know how to stab without hitting an organ.

That is - in order to make fun of someone without actually hurting them, you have to know which kinds of topics not to touch for any given friend. You skip the "your mom" joke for the friend with parent issues, and so on.

On the other hand, though, I have very often see my fellow enginerd types badly misread this dynamic. I've seen guys come onto an established team where some mutual teasing has evolved, then fall flat when they try to emulate that it - because they haven't yet earned the depth of relationship that makes it OK.

It kind of reminds me of another "nerd social fallacy" I've often observed, which I guess I'd name: "I can't be a bully." I think a lot of times people who've grown up dealing with bullying don't realize when they've become one. Sometimes the mutual teasing degrades into one guy just being a dick to the other.