If some or all of the URLs entered are already whitelisted, the results page from the first "SUBMIT" einforms you, in tiny type, that "These URLs are already alive or have since been whitelisted and will not be reported:"

Perhaps, if you enter a URL on the "To begin, type in any number of (non-archive) URLs, you wish to report as false positives. Place each URL on a new line. Please only type in URLs. This is an automated process." page and click SUBMIT, and some or all of the URLs have already been whitelisted, the page should show something such as

These URLs are already alive or have since been whitelisted and will not be reported:
http://example.com/first-url-that-wont-be-reported.html
http://example.com/second-url-that-wont-be-reported.html
    ...
http://example.com/last-url-that-wont-be-reported.html

Please review the following URLs and confirm that they are really not dead:
http://example.com/first-url-that-will-be-reported.html
http://example.com/second-url-that-will-be-reported.html
    ...
http://example.com/last-url-that-will-be-reported.html

with the headers for each of the lists in boldface, to make it clearer that some URLs will not be reported as they're already known to be OK. If one of the two sets of URLs is empty, its header shouldn't be displayed. If the "Please review the following URLs and confirm that they are really not dead:" set is empty, the "SUBMIT" button shouldn't be displayed.
This will improve the usability of the false positive reporter.