What is "Less Sodium Soy Sauce"?
Well, this is what Kikkoman has to say about it:


  Kikkoman Less Sodium Soy Sauce is brewed exactly the same way as all-purpose Kikkoman Soy Sauce. However, after the fermentation process is completed, approximately 40% of the salt is removed. Although there is less sodium in Less Sodium Soy Sauce, all the flavor and quality characteristics remain because it is aged before extracting the salt. However, to maintain this full flavor, we recommend using it during the latter stage of cooking in braising sauces, soups and stews, vegetables or stir-frys.


Huffington Post claims otherwise:


  Another category of soy sauce is low-sodium, which is made with extra chemicals. Cooking instructor and author of "The Chinese Takeout Cookbook" Diana Kuan recommends diluting regular soy sauce if you want less sodium instead of buying the low-sodium stuff. 


The ingredient list on my Kikkoman Less Sodium Soy Sauce includes lactic acid, which is not on the ingredient list of Kikkoman Original Soy Sauce, but as it is a by-product of fermentation, I'm not sure that it means anything.