User blog comment:DaNASCAT/Technical Update: November 23, 2015/@comment-5973717-20151124052723/@comment-5558012-20151125213411

While the functions are similar, the two environments are a little different. Some people have no interest in chat, others have no interest in threaded discussions. One's a little formal, the other casual. One is logged, the other isn't.

I personally don't think they should be merged into one group as they are different for the reasons above and, arguably, might have divergent ideas, environments, and policies of what's acceptable.