1) Writing and Speaking by Paul Graham is a relevant read.

2) As others have said, X isn't about Y. Conferences aren't about discussion (personally, I don't really know that that's true; I'm basing this assumption on my hearing lots of other people saying it).

However, I still think there are important questions left to ask:

3) If the goal of conferences isn't discussion, what is it? I suspect that conference organizers aren't really asking themselves this question, and that they're suffering from Lost Purposes. How do stronger (social) relationships lead to more scientific discovery? Is it trust? Informal discussions? I think that science is really really important, so even if the marginal improvement to conferences is small, I sense that it's multiplied by a big enough number such that the marginal improvement itself is also quite important.

4) Even if the goal of conferences isn't discussion, discussion is still something that's really important. "How can discussion be optimized?" is a really important question (similar logic to 3). As to your question of how discussion could be improved, here are some initial thoughts/brainstorming (nothing novel or too useful though):

• In person discussion might not be best. Well, I think there's a place for it, but I think it often takes a lot of time to think before you respond. There are a lot of benefits to communication via writing over communicating in person. My impression is that it should be the main way to have real discussions about difficult things (I'm not in academia, but I'd guess that it already is).
• But if you're going to have in person communication...
• I sense that groups of 2-5 are probably best. In my experience, there's too much friction in bigger groups. I wonder if there's any research on this?
• I think it's really important to diagram things out. In my experience, people either a) don't think to do that in a conversation, or b) are too lazy to do it. Yes, it's not always appropriate because it slows down the flow, but I think it's appropriate to do a lot more than it's currently done.
• I think there's probably some interesting uses of social pressure and "pushing people's buttons" to motivate them (think basketball coaches like Phil Jackson).
• Maybe use some sort of technique to establish group cohesion. Working together to solve a common (short-term/pressing) problem? Fight a common enemy?