FWIW, if you use all RO like I do, the Na from baking soda doesn't get excessively high in dark beers. I have a pretty roasty American stout on tap now and the finished Na level (from baking soda) was ~ 40ppm, well under Martin's Brunwater limits. It's a good beer. But I definitely wouldn't want to use baking soda with any tap water, softened water, etc.