Collapsible

Agaric wants:

agaric: We have some users who would like to expand and collapse comments with ajaxy little plus and minus signs rather than the default all or nothing comment option.
[8:02pm] agaric: Is there a module, or theme snippet, or generally known solution hiding itself from my searching skills?

drupal collapsed comments
drupal theme collapsed read comments

thanks to Gurpartap on #drupal-support:

// but this is for all the comments at once- selectively expanding one at a time or a sub-thread is not supported with this as is...

if (arg(0) == 'node') {
drupal_add_js('$(document).ready(function() { $("div#comment").hide().slideToggle(); });', 'inline');

}