That is essentially what happens and it's a technical issue, not a philosophical one. If one instance is denied posting to another, the user should be notified at some point about that. There are a lot of silent errors right now with the setup. If you disable signups for example, users can still try but never see that it will never work.
Nice! Worked like a charm. For anyone having issues with using a bookmark to run javascript, you can paste it into the developer console!