Let's choose a package tha is a candidate for upgrade (previous testing
version is installed, and more recent than current stable version).
If I select it for upgrade to testing and quit aptitude, the selected
version is still selected when I launch aptitude again.
Now if I select it for downgrade and quit, then on next launch
not only the downgrading choice is lost, but the package is now selected
for *upgrade*.
Combine this with a bug like #874012, where for some reason it seems to reset
selections as if user had quit and relaunched, and a time-consuming
selection of packages while attempting to restore a broken situation
just gets frustratingly lost.