Views - arguments code to filter out comments by auther of node

I have a block display view of comments on a page. I have Node ID from URL argument to limit comments to those for the node being viewed. I want to filter out comments made by the author (user) of that node. Can't figure it out...

In the opposite use case, where I want ONLY comments from the author of the node, this works for 'Provide default argument':

$node = node_load(arg(1));
$comment_user = $node->uid;
return $comment_user ;