Addendum to: A simultaneous Frobenius splitting for closures of   conjugacy classes of nilpotent matrices, by V. B. Mehta and Wilberd van der   Kallen
  Prompted by an exercise in the Brion Kumar book on Frobenius splittings, we show compatibility with a few more subvarieties of the Frobenius splitting from our 1992 paper. 
Wilberd van der Kallen