Polishes and Brasso are by their very nature abrasive. While they MAY not actually take off metal or materially affect the sound of most cymbals, I would personally stay away from using any abrasive product on my relatively large and valuable cymbal collection. To me it would be as inappropriate as using Pledge furniture polish on a Stradivarius! I remember reading on a site where there was a recommendation to use Carnuba car wax on a cymbal after cleaning to restore the original shine. Seems most folks desire to restore their cymbals to like new, and have little concern with the effect on the sound. Perhaps with rock in louder venues that's not as important. But with jazz, cymbal subtleties make a difference musically. Its a personal decision. Like doctors, my credo with vintage cymbals is "do no harm". I only purchase cymbals that in my estimation sound great. I buy them to use and not just look at. I do nothing that might alter the sound in any way. I once cleaned a 16 inch crash cymbals for my son a number of years ago when I didn't know better. It was a wonderful mellow crash and after cleaning it sounded brighter and a bit harsh. My son noticed the change in sound first and still refuses to use it to this day even though he performs a couple of times a week. I used Groove Juice and I learned the hard way.
With all due respect-Let's talk a moment about the beautiful words like "patina" and "natural". I beg to differ,but cymbals are shiny when made and darken from oxidation over time!If the material were iron or steel,an engineer would call it Rust!It looks worse,and the metal is altered from original.That doesn't improve the structural integrity of a bridge or a car fender.It's a by-product of being exposed to air! I don't confuse my cymbals with wine which is stored away from air! Yes, polishes remove material-you can see the black on the rag...If you like 'em clean, use low-abrasive silver polish,not muratic acid or Groove Juice. Muratic acid was meant as a concrete driveway stain cleaner.
Again-I'm not an audiologist nor metallurgist,I just don't "Drink the Kool-Aid"! My Zildjian As and Ks sound fabulous! Cymbal characteristics are derived from 3 things: Heat,Pressure(Hammering)and Alloy. I repeat my respect for other views.-the Heretic.