Cleaning Coins And Value.

There is no one answer for all the reasons you have already pointed out..

Ultimately, it's your coin, and if you like your coins bright, shiny and blemish-free, do whatever pleases you.

But yes, as @john says, there will be some risk of reducing the value ("destroying" is a bit harsh for the gentle treatment you describe) depending on the outcome.

Caveat lautus.

Every coin recovered from burial needs to be cleaned.
That has happened to most ancient coins.

Conversely, if a coin does not need to be cleaned, then don't clean it. Simple.

We often talk about "good cleaning " and "bad cleaning". By which we actually mean "market-acceptable cleaning" and "market-unacceptable cleaning". The main difference is whether or not the cleaning is visibly evident on the coin itself afterwards. A soak in acetone is market-acceptable, when done properly, because it doesn't alter the coin's surface at all. Rubbing the coin with one of those silver polishing cloths is not market-acceptable, because the coin is visibly scuffed and scoured by the abrasives in the cloth.

The example given by the OP is illustrative of why "common sense" is a poor indicator of what constitutes "good cleaning". A "microfiber cloth and distilled water" sounds harmless, but there are circumstances where it isn't. While the microfibre cloth itself indeed should be harmless, the problem occurs if the cloth actually picks up any dirt or debris as it is wiped across the coin. This debris sticks to the cloth, and each piece of stuck debris then gets scraped along the surface of the coin along with the cloth. This can leave a scratch-line, which would be clearly visible if we're talking about a proof or high-Unc coin, as the human eye is drawn to defects if the actual number of defects visible is low.

"Bad cleaning" always damages a coin, and thus always reduces the value, because you reduce the demand for that coin - there will be future potential buyers of the coin who look at it, and decide not to buy it because of that cleaning damage.

How much it reduces the value by, generally correlates to how old the coin is. Old coins have had much more history, and are thus much more likely to have been cleaned by a well-meaning custodian at some point in its past. The high proportion of surviving coins that have been cleaned means that such coins still retain some value and interest to collectors, though still less demand than for uncleaned coins.

Thus, consider German thalers, hundreds of years old and popular with the European aristocracy ever since they were first minted; almost all of them have been cleaned at some point, by somebody, usually over a hundred years ago; so the "penalty" for "old cleaning" on a thaler is minimal, unless it's a really bad cleaning job or otherwise makes the coin look especially ugly.

Modern US Mint NCLT commemoratives issued in the last few decades, on the other hand, do not have that history, and most of them are residing either in slabs or are still sealed up in their original Mint packaging; they shouldn't need cleaning yet, and haven't have had time yet for lots of them to have been cleaned, thus the value penalty for actually cleaning one is quite severe; a poorly cleaned NCLT commemorative is usually reduced to bullion value, and will likely get melted down, simply because literally nobody wants a coin like that.

Well said, @Sap.

I learned my lesson about 55 years ago. I'd started collecting Lincoln wheat cents, all from circulation. I had managed to fill a lot of holes in my Whitman album. Dad was in the Navy and used Brasso to keep his insignia, belt buckles, etc. nice and shiny.

I still clearly remember thinking "That'll sure make my collection look nice!" Well, needless to say, I polished them all up to the point they were just gleaming, and proudly showed them to an older kid who'd been collecting longer than I had. He proceeded to tell me I'd just ruined all my coins, and explained why. I then took it upon myself to learn about the proper handling and care of coins, so it actually turned out to be a good (and inexpensive) lesson for me...

Dearborn, I suspect that for a lot of us who started collecting at an early age, that particular "learning experience" was not an uncommon one!

Who among us has not ended up with some "Pepto Pink" Lincoln cents in their possession?