Just empirically, I know that a lot of folks hiking longer distance believe in the adage of "tank up and camel up" at water sources when hiking in relatively warm weather when water sources are far away. 'Tank up' being to fill water bottles, and 'camel up' being to drink as much as you can at the water source.

I'm uncomfortable with the idea that this suggests "drinking till you're bursting at the seams", however. It often includes stopping to eat a meal near the water source (particularly if shade is to be had or can be created). If a person has arrived at a water source somewhat dehydrated, I think they can suck down quite a bit without ill effects. And I would suspect that the ill effect would result in enough discomfort that would alter how or if a person could hike, hence I suspect this is somewhat self-regulating. Again, just empirical, no medical background for me. But I remain a believer in the adage, tempered as always by common sense and "listening to your body".

I've never met anyone who had hyponatremia. Indeed, most foods seem to have an overabundance of salt, and folks that hike the way that I do tend to be eating a bit as they go along.