Thread:Project:Support desk/Hide paragraph with UACL/reply

Extension:NamespacePermissions has security issues. You could use Extension:Lockdown to hide entire pages belonging to specific namespaces, but Extension:PrivatePageProtection seems more suitable for your case. You should place the 'secret' content in a separate page, alongside with the allow-groups parser function (e.g.  for administrators). I don't know if that extension also forbids viewing content transcluded from read-protected pages.