I've found MathOverflow [1] to be the best high-level math discussion forum out there right now. Many prominent mathematicians are regular posters, and I think the question-and-answer format suits mathematical discussion very well.
It's also just not meant for discussions; if there are more than a couple comment replies, they "move it to chat", which I've never used.
Specific forums or subreddits can often have good discussion, but often not as much traffic.
If the StackExchange sites provide an allied discussion forum where I can specify what level of users I want posting on my thread that would be great.
Where level can be verified grad/phd in subject X or anyone who has more than N accepted answers in subject X...
Come on CS folk make it happen.
Right now I have to wander around labs and conferences to find the right people and have these discussions. A gigantic waste of time when most of these folk hang out on MathOverflow but can't have these disccusions.
Most of the progress in science came through 2-3 people finding and corresponding with each other. Here we are at a moment in time, where we don't need to find just 2-3 people.
We can find ever single one whether they are sitting in Cambridge or Congo and lay out a subject before them and yet we haven't got that to work right.
I think if you asked most academics their opinion on this (in math/CS at least), they'd tell you they think the system works fine. They don't really have problems collaborating - their universities send them to conferences where they meet people working in the same (narrow) subfield as them.
I think this is a matter of preference. I see where you're coming from, and there's a lot of value in that kind of unrestricted brainstorming, but I've always preferred to have those types of discussions in person with some whiteboards available for fleshing out ideas. When I'm brainstorming, I don't want to get caught up in LaTeX formatting issues, or to spend an hour writing out a response, only to have the discussion go in a completely different direction within that hour.
I enjoy reading MathOverflow because the Q&A format forces the question asker to take whatever vague idea they have and form it into an objective question that can be rigorously proven or refuted. The narrow focus keeps the discussion on topic, so even if it takes you a while to contribute, you can be assured that your response will still be relevant.
Not everyone has people to talk to in person that understand their subfield. In a small institution it might be 100 miles to the nearest person who could converse fluently in what it is you're thinking about, even if thousands of them exist.
It’s true that there’s lots of discussion that is out of the scope of mathoverflow which doesn’t have a centralised place to go on the internet. Such discussions tend to live on blogs and forums and email lists and discussions at conferences