I have noticed that the comments in slashdot, while often SPAM, have a much greater quality than those at digg. Slashdot can often have comments vastly more intersting (and informed) than the article the thread is about, while Digg often has few worthwhile comments at all.

Slashdot does, however, need to work on the duplicates, spelling, and quickness-of-posting problems that Digg has gained popularity with.

Mirwin.net