In the first version of the manuscript, we used to control convergence
with an energy norm where the elasticity part was scaled with the
residual stiffness 'k'.  As far as I remember it this wasn't really
intentional, but the matrix for that norm just "happened to be
available".

When we started to implement the operator-splitting algorithm we wanted
to consolidate the convergence criterion, and we replaced the scaled
energy norm by the true energy norm.  As it turned out, this
overestimates the error in some situations where there is a complete
crack.  This is particularly noticeable for the models with spectrally
split energy, for reasons that we don't quite understand.

This patch puts the scaling back into the norm.  From a theoretical
point of view the scaled energy norm is not worse than the unscaled
one, but the iteration numbers look much better this way.