How do I go about restricting access to a topic or forum only to non-approved members? That is, members who are registered and all that, but whose applications I haven't approved? I haven't the foggiest idea if this is even possible, but if it is, I'd love to know.

You can't restrict the topic, but you CAN restrict the forum. You need to set them up under a separate forum mask, and restrict their access that way.

ACP -> Forum Control -> Permission Masks

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