hi
since both nodes and comments are exported through sioc,
why not add the has_reply property to nodes and reply_of to comment?

this should be handled in way that a comment of a comment (comment thread) should point to it's parent comment of course.

have a blast
rackoon

p.s.
also posted on drupal.org - http://www.adamtibi.net/sioc.axd?sioc_type=post&sioc_id=81867dd9-ba89-447b-928d-124c6df4a957