A very very faint possibility of Trinitrees
suggestion being testable. If good colour
measurements of stars surrounding the 1987a
supernova were made in the months afterwards,
any reddening due to passing through the shell
of neutrinos could in principle be seen. This
would be in space yet to have the expanding
debris.

But then I have made this suggestion before in
relation to gravitational waves and I do not
think you thought much of the chances.