I think BrowserUK was trying to approve the post. I've tried to approve this also, it fails. IIRC there was a problem approving nodes once they'd been moved from another section.

Likewise will not allow approval by me.

Approval has nothing to do with posting replies. If you look in Recently Active Threads you'll see a (U) next to the post.

Alternatively, if you have the Approval nodelet enabled and you view the root level post, you'll see the '()approve' checkbox next to the '()frontpage' checkbox. Unlike the case if you view the OP of this thread where you'll see the annotation that marto approved my post.