Are cataracts noticeable to other people?

Usually not: Until the cataracts are extremely severe, which at least in the us is quite rare.

Not usually: If the lens of your eye becomes completely white with a very advanced cataract, the whiteness can be seen through your pupil. So instead of your pupil appearing black , you will notice a white reflex filling the pupil of your eye. Most cataracts in the us are removed before they reach this advanced stage of development.

Usually no: Unless very mature & hard & very white, most people do not notice a person's cataract.