Digging down comments.

[Spike Lee]

That ability to digg down comments is a much better one than censoring or deleting.
Note that digg uses it.
http://digg.com/television/Last_Week_NBC_Had_Its_Worst_Ratings_In_History_Pro bably

[hanpil]

It's also been implemented on Youtube and Digg's partner, Metacafe.

[hardXcorey]

Ebaumsworld already uses it.