I have never really used StackOverflow, so from just a casual observer's point of view: It seems that allowing discussions would deviate the site into another c

I have never really used StackOverflow, so from just a casual observer's point of view: It seems that allowing discussions would deviate the site into another commodity forum (there are already hundreds on the topic of programming), at which point they've lost their marketplace edge. I suspect they are trying to protect against that.