This isn't too much of an exploit, since you need Creative mode to use it but it's a bug nevertheless. The walls cannot be broken normally with Creative mode instant-break, but if they are warded with the Wand Focus of Warding they become a special Thaumcraft block, which can be instant-broken to leave holes in the walls. They are still unbreakable in Survival, so it's not too big a deal.

Won't fix because creative mode only. I would have to make the blocks have TileEntities. Not happening.