Which hook to allow specific users to add/edit/view comments? Is there a hook that I can use that would give specific users permissions to add a comment, or edit their own comment?  I was hoping there would be something like hook_node_access().

In my form, I have a select list with all the users that the submitter can choose.  If the person is selected, then that selected person can comment on that specific node.  

I looked at the comment access module, but that does not work since it is still being controlled by role permissions.
There is no hook to do this. One possibility that doesn't require editing of the comment module is to change the comment status of the node depending on the current user using hook_node_load:

function MyModule_node_load($nodes, $types) {
    global $user;
    foreach($nodes as $node) {
        if(!user_has_access_to_node($user, $node)) {
            $node-&gt;comment = COMMENT_NODE_HIDDEN;
        }
    }
}


The hook will be called after the one in comment module, and will prevent users from posting comments unless user_has_access_to_node returns true.

The implementation of user_has_access_to_node would simply check if the current user is in the list of users allowed to edit the viewed node.