I can see why the idea of the spell making things brighter got started but I think it is an absurd interpretation that isn't really supported by any other aspect of the spell (including the name). In fact, its descriptor [Darkness] indicates that it cannot make anything brighter. In order to make something brighter, it would need the [Light] descriptor.
IMHO, there is no fix needed on this spell unless you rule's lawyer it with a "strict interpretation" of the wording. There is no verb for what darkness does (illumination is based on illuminate which is what light does), since strictly speaking darkness isn't a thing and can't do anything. The word illumination was chosen but perhaps "emanation" should have been chosen.
DC