Synapse is the best tool for long-term complex discussions.
Synapse is developed for busy people. It's purposed to get things done, mitigate the inevitable mess during large conversations, and focus activity in the right directions by explicitly outlining the discussion structure as it evolves.
How it works
You organize everything in rooms. Typically, single project/discussion takes place in one room (compare to a series of related emails). You add users to the room and create messages there. You can organize messages in a hierarchy with up to 3 levels.
Don't forget to check out getting started! Click Start button right after installation.
Search charm requires Pro subscription. Everything else is available for free.
Keywords: chat, email, messaging, collaboration, discussions, note taking, task management, project management