humans are big membrane enclosed bags of mostly water, but also fats, proteins, etc. And some salts including sodium-salt. According to what I keep reading, none of that other stuff matters, only the sodium-salt and the water. Add a little salt to the big-garbage-bag-that-is-a-human, we are told, then you must add a ton of water to keep the salinity the same. How much? Till you are pissing clear, you're not done. Your body magically keeps every thing else in balance, but you need to manually intervene by overconsuming water. And I just don't believe this could be the case, it's just the "drink lots of water" meme repackaged.

"what is the harm" or "why" is never addressed.