"Including this one" is a good example, for how the rules of how content is selected for presentation define the medium. Even with exactly the same people, exactly the same dang occasionally nudging people this way or that way, this place would be an entirely different if the effective feed composition wasn't the one it is. So much of the identity of these online communities is an emergent consequence of the mechanisms employed.
Then on the other hand, I know of some off topic situations that I consider very valuable, because any forum set up specifically for the topic in question would draw a very different audience.
