I think only palisades and motte-and-baileys/townslands (and I'm uncertain on townslands). Higher fortifications should not allow digging in. When I first stumbled upon digging in even with palisades and motte and baileys, I thought it was weird. I don't know why its allowed or if its an oversight/bug that should be fixed.
Agree. I think it should be fixed to make it more consistent.
