So you want to have comments which will be visible only for their author? I do not know how to make this for certain category or object but I can explain how to make this for whole site.
You have to:
1. Open file /components/com_jcomments/model/jcomments.php
2. Find line:
$where = array();
and add after:
$where[] = "c.userid = " . $acl->getUserId();
3. Find code:
$query = "SELECT count(*) "
."\nFROM #__jcomments "
."\nWHERE object_id = ".$object_id
."\nAND object_group = '".$db->getEscaped($object_group)."'"
and replace with
$query = "SELECT count(*) "
."\nFROM #__jcomments "
."\nWHERE object_id = ".$object_id
."\nAND object_group = '".$db->getEscaped($object_group)."'"
."\nAND c.userid = " . $acl->getUserId();
This modification will restrict comments viewing by only user's own comments.