I'm actually divided about this. On the one hand, it's a really good point - this isn't something which should be a commitment. On the other hand, it makes sense as a norm - it's worth a lot to see an argument end in a satisfactory fashion, even if that fashion is, "I don't see any value in continuing this debate".

On the gripping hand, though, people will drop out of arguments without conclusion - through burning out, getting slammed with other commitments, or even through the simple decision that the community is not worth their time. And all these are legitimate reasons, even if "I can't win this argument otherwise" is not.

"Encourage it" is about where I'm at, now.