Hi Jeffro,

I'm pretty sure this field has nothing to do with the plugin. I have it in my DB and I've never installed the plugin.

The field is used in the core code: on line 894 (in 2.8) of wp-includes/comment.php which is called when comments are inserted into the database and also on line 1115 when comments are updated.

If the field isn't in the DB, then WordPress will fall over when a new comment is made or an old one is edited.

I would guess this is a field they added sometime back with the idea of one day creating a feature which used this (much like the comment_parent field was added many many versions before WordPress added threaded comment support to the core).