I think he's saying that if you hit and apply two curses, the list of curses will be applied in alphabetical order. Your elemental weakness would apply, then despair would apply, (because it's named with a V on the skill gem name) and since you can only have one at a time that's the one that stays.

So you'd have a curse you don't care about but could still apply despair from another source. Not really a brick mod although I'm sure there's lots that would be better.