To elaborate further, the sheer absence of the blue-green, "arguments are soldiers" mentality which previously abounded (no doubt helped by the fact that everyone had a large set of shared core premises) made every conversation seem like a step forward. People did nit-pick excessively just as we do today, but somehow it felt like the good kind of nitpicking..

But it's not that people were nicer or more diplomatic. They were a lot more playful back then, but they would still be fairly blunt even by internet standards. It was something else...I think it was simply that they were more interested in getting to the right answer than they were in "winning" in the rhetorical sense.

I guess to put it dramatically, LW has gradually been consumed by the Dark Arts, which has caused a lot of quality people to get bored and leave.