occasionally, multiple watches exist in our installation for a given page for a given user.

One way to make this happen is to right-click and copy the url for the 'watch page' icon, then paste it into the address bar and navigate multiple times to the notification action for that page id. I don't think it's limited to this, however, as it is quite frequent in our installation to have duplicate watches for some users.

relates to: http://developer.atlassian.com/jira/browse/CONTRB-33