Movable comment system

I love the comment system invented by those guys at reddit.com. It's a genuine innovation by bringing together a couple of simply ideas, resulting in an elegant way of visually structuring a conversation.

Reddit started with the idea of ranking comments, form sites such as slashdot and amazon. Each comment in a thread is scored, whereby comments in a thread can be rated with an unobtrusive up-or-down arrow. The innovation is that the comments in a thread flow up or down a page in terms of the comment rating. Those that are popular float to the top of the page, and those that are unhelpful sink to the bottom.

It's a remarkably intuitive system that rewards good contribution to the conversation, without resorting to draconian censoring measures. Bad comments are not hidden; they just sink to the bottom of the page. If you feel inclined, you simply scroll down to the bottom-feeders and see the shit. Good comments are not just rewarded just by brownie points, but they get to be read first simply in lieu of being at the top of the page. This provides a genuinely useful service for other readers.

Having threaded comments is also important. Replies to specific comments get attached to the parent comment, and they move up or down with them. However brilliant rejoinders to a shitty comment deserve their day in the sun, and whole threads get moved up if the replies are rated higher than the parent comment.

On reddit.com, the cream does float to the top. But if you really want to, you can still lick the scum at the bottom.