Destroy Wall only affects orthogonally adjacent objects, as does punching. Diagonal is not adjacent. This will be in the next FAQ.
I know the text on Destroy Wall specifically excludes diagonal adjacency, but, in the manual, punching is defined as:
A wizard may punch another wizard in his square or in an
adjacent square to deal 1 physical damage. This attack does
not require a card, but it does count as the wizard’s attack
for the turn.
And the Adjacent target range icon on a spell card is defined as:
Adjacent: The wizard may play this card only on a target
that is in the same square as himself or an adjacent square
(even diagonally adjacent). The target must also be within
the wizard’s line of sight.
So are you saying this adjacency definition, which includes diagonal adjacency, applies only to spell cards with the icon and not to the act of punching (i.e., orthogonal adjacency only)?