Cursed potions of invisibility remove any permanent intrinsic invisibility you have, but still give you the normal cursed duration of temporary intrinsic invisibility, so after that duration you will become visible again. Thus, they are a controllable way to remove the permanent intrinsic and are also still useful for characters without invisibility yet.

Quaffing cursed invisibility removes the invisibility intrinsic if you had it. Possibly the same for see invisible.