While a difficult by nature thing to define (even its proponents don't know exactly what it is), there are certain things that are characteristic of post-moderns.
One is a love of the "conversation." Some think that po-mos don't beleive in absolute truth, but that's not quite true; they just want to talk it over and see if we have it. They will talk and talk and talk. They will inject irrelevancies and needless levels of complexity in order to keep the discussion going. In a way, it is wrong to say want to have disucssion about issues, since they don't really engage in discussion for the reasons most of us do: to arrive at an end. For most folks, conversations are means to an end, but in po-mo thought the conversation is elevated to being an end. They don't want the discussion to end. In a discussion about truth then they won't let you say you have truth, not because they don't beleive it exists, but because you would be ending the discussion, in thier eyes, preamturely (though it is not clear whether they think the conversation should ever truly end).
Now this is a bad thing. Not that I am opposed to conversation, I enjoy a good chat. But when complexities get added constantly and irrelevancies and rabbit trails are exalted to the status of core issue then I am not having a discussion. As I said, discussions have a goal in coming to agreement and resolution. Po-mos just want to keep you talking.
Now you don't have to be young to be like this. Nor do you have to be self-consciously post-modern to engage in this behaviour. I suspect a lot of peopel aren't aware. So do thema favour and let them know.
Let them know that keeping the discussion going by inserting extraneous detail is actually opposed to what you understand to be the goal of a discussion; ending it with an agreement or other resolution. It can't go on forever, and not every point is worth discussing at length or even at all.