Speed up loading via “Read More” button

To speed up loading of pages, Yahoo has a Read Full Article button (if that page can’t be seen, here’s an image). Question: how would one support that with WP for a page full of comments? Would like to load just a few of the most recent comments, and on clicking of a “more comments” button, load all the comments. Page has a video — playing of video must not be affected by loading of rest of comments.

Thanks