I have several stainless steel staples in my chest from open heart surgery, and I later had several MRI’s no noticeable effect from the magnet though.
Most stainless steel alloys are not magnetic, a discovery that greatly annoyed my refrigerator magnet addicted sister upon completion of her kitchen remodeling frenzy.
I enjoyed much mirth and merriment at her wrath upon my cluttered ‘fridge door hating, aircraft mechanic brother-in-law, who understanding why compasses are mounted with brass or stainless screws, slyly endorsed her selection of stainless steel appliances.
As you noted, current surgical staples and clips are almost invariably stainless steel, with a very low or non-existant magnet pull. Irregardless of the the type of metal, overexposure to a MRI magnetic field can still cause magnetic eddy currents which result in heating of the metal in question. In a normal study this typically is not a problem, but it can be a POTENTIAL issue with extended exams in high strength fields.
Those with tattoos should volunteer that information as many tattoo inks incorporate metallic compounds. The potential discomfort from heating can be alleviated with the use of cold compresses if the the technologist knows of them.