Hi Ad:
First, to remove all allowed namespaces, add the following line in the SiteSpecificConfigurations.php file:
unset($wgPageAttachment_allowedNameSpaces);
The reason being, the way PHP works is that when you do the following, you are actually adding new values to the array and not clearing the existing values.
$wgPageAttachment_allowedNameSpaces[] = '';
Second, suppose you want the pages in category "DOCS" to have attachments, then add the following line in the configuration file:
$wgPageAttachment_allowedCategories[] = 'DOCS';
Third, to allow specifying dynamically which pages should have attachments by adding "__ATTACHMENTS__" token in the page, add the following line to the configuration file:
$wgPageAttachment_allowAttachmentsUsingMagicWord = true;
Fourth, in case you want to change __ATTACHMENTS__ token to something else, perhaps to __AA__ to shorten the token to mean "Allow Attachments" then add the following line to the configuration file:
$wgPageAttachment_magicWordToAllowAttachments = '__AA__';
Let me know if the foregoing resolve your issues.
Sincerely yours,
Aldrin