Some sensible advice about cleaning coins, if necessary, has emerged. To communicate this to newbies, it may be best to instead of quasi-scientific platitudes, to use simple, everyday, language.
I'd be leery about cleaning with dish soap. It's got really strong detergent in it and can react with the metal enough to slightly change it's color which is also enough to devalue the coin. Cleaning coins is like scratching a mosquito bite... only makes it worse.