I think that Slashdot overall still has the highest quality comments. You just have to sort by score, and do a -2 funny modifier. The site instantly becomes much much better. Stay away from the new ajaxy score slider system.
>>foonam+(OP)
Interesting. I wonder how Slashdot maintains a high level of commenting over time. Thanks for the tip. Perhaps I'll revisit them in 18 months...