I don't think it's necessary outside of being a good treatment for many diseases, but I don't think a constant low dose would be harmful. Unnecessary for sure IMO, but probably not harmful.
Agreed. People will argue this until they are blue in the face. Use critical thought, many people dont use it and have 100% healthy tanks. For example, ive never used it and havent had a sick fish in a year and a half. Good water parameters will do more for your fish than salt ever will.
"The simplest explanation for some phenomenon is more likely to be accurate than more complicated explanations." -Occam's razor