[susam]

There are still tight-knit communities on Freenode IRC and Reddit. For example #lisp, #emacs, ##math, r/lisp, r/emacs, and r/math have great communities with friendly attitude.

Stack Overflow operates at a much larger scale and compared to Stack Overflow, these communities are definitely much smaller but I see that as an advantage. The quality of discussions is often pretty good. Off-topic friendly banter occurs once in a while when the channels are quiet. With a good percentage of the members composed of regulars in these channels, they are still able to maintain a sense of community.