I suspect that if we imposed a norm on LW that said: every time two people disagree, they have to write down, at the end, why they disagree, we would do better.

Unfortunately that is usually 'I said it all already and they just don't get it. They think all this crazy stuff instead.'

Just letting things go allows both to save face. This can increase the quality of discussion because it reduces the need to advocate strongly so you are the clear winner once both sides make their closing statements.

Imposing a norm would add a lot to the effort involved in conversation. Every time you thought about engaging, you'd know you'd risk having to figure out a conclusion. This might or might not be a net win for signal to noise.

Sometimes it takes quite a while to figure out what the actual issues are when new ideas are being explored.

Instead of a norm requiring explicit conclusions, I recommend giving significant credit when they're achieved.