Don’t forget that you can use the soft selection to delete a particle once its crossed a randomized per-particle selection threshold, which makes it more than a simple boolean. Whether anyone actually needs this is a different story.
I think the most prudent solution to your scenario is to (optionally?) have the Krakatoa Delete modifier reset the Selection channel to 1 of particles that weren’t deleted. I’ve also toyed with the idea of making a modifier that combines the selection and delete step into one, where the output node is forced to be a bool/float nameless channel that determines if that particle is deleted. This requires a bunch of refactoring of the KCM editor code so I’m leaning away from it at the moment.