get_collapsed_commnts in Client.pm

"link_id" is the ID of the link the comments are under.

"children" is a reference to an array containing the comment IDs.

If "limit_children" is true, return only the requested comments, not replies to them. Otherwise return as many replies as possible (possibly resulting in more MoreComments objects down the line).

"sort" is one of 'confidence', 'top', 'new', 'controversial', 'old', 'random', 'qa', 'live'. Default seems to be 'confidence'.