I spent a lot of time thinking about this the other night, and I believe I found a very believable reason why this forum is so nice, aside from the learning curve turning most troll-type posters away.
Anybody who plays this game past the initial learning stage and actually gets to the point where they "understand" the game has come to terms with the fact that you cannot win DF. With that being said, there's no competition. Without being able to win, and with a game thats so diverse, there's no reason to compete. There is no right way to do anything in this game.
An example of this would as simple as something as embarking strategies. There's no need to fight over petty things such as which embark skills/goods are the best, because in the hands of a skilled player, you can embark without any skills and just a log of wood and build a decent fort just fine.
I guess what I'm trying to say is that instead of arguing over whats "best" so that we can "win" better than anyone else, we all help each other see new and creative idea's that allow us to play the game in a different way. I've not seen one person on these forums claim to be a better DF player than anyone else, I've just seen them say they have more experience, or that they've come across said problem before and then listed how they overcame it.
I personally believe that the "Losing is fun" mentality that all DF players have is ultimately what sets this community apart from all others.
Now if you'll excuse me, my woodcutter just got done with his strange mood, and he's beating all the cats to death with the yellow jasper table he crafted.