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Collapsible Comments plugin provides an easy way to make all comments to collapse and expand inline with an excerpt at every page or post. You can set the number of characters that will be shown for each comment and after clicking a link, they will be expanded. You can also specify the style by editing a simple line. Collapsible Comments is tested on Firefox, Opera, Safari and IE 6 & 7 and works without problems.

So have fun and keep blogging!