Basically I want to clone the comment system of sites like digg or netscape, where users can rate and filter comments.

I understand that it has to do with AJAX, maybe you can give some pointers, links to some basic scripts from which i can learn? That would be great!

I have a problem visualizing a proper method of hiding showing comments without reloading the page, so any advice would be appreciated

You can see what I'm talking about in this video: youtube.com/watch?v=c8A80qjgAS8

My guess is that all the comments are loaded with the page, but comments with a lower rating are hidden.

So basically the dialogue is one sided: you press thumbs up/down and your vote is being sent to the server, but the server does not return updated information until you reload the page

Most of what one can see in that video is done on the client side by a javascript, am I right?

And for example if I make a dropdown box where a user can select the lowest rating value below witch the comments are not displayed, all this "filtering" is done one the client side using javascript?

If so maybe someone could point to where I could find some similar scripts, as being used in this video