If you have "show unmoderated content" set, you still see the node in the reply list with "This node has been reaped" (or similar; I forget the exact words). I was wondering whether an option might be added to just not show those nodes (or their replies) at all.
OK, if now, the reaped nodes don't show, if 'show unmoderated' is _not_ set, then most of the machinery to accomplish what you want should already be in place -- which supports you're "I don't think it would be all that much work.." hypothesis a few re:'s up.