Flavor – Sweet = Sugar, Salty = Salt, Sour =

I've noticed that salty food has somewhat of an addictive quality; people who eat a lot of it (i.e. fast food or other processed food) tend to bury their meals under a mountain of salt, whereas people such as myself who do a lot of home cooking hardly use (or want) any.

"Season to taste" means pretty much what it sounds like; add however much salt (and other spices) that you, personally, like the taste of. If you have a habit of eating a lot of salty foods, then you might want to add a little less than that, for the benefit of people like me who gag at heavily-salted foods.

If you use a lot of other spices, you won't need much salt - a few shakes of the shaker is enough. If the food is basically bland aside from the salt (and maybe pepper), then you'll need to use more. The best thing to do is add a little, then taste, and repeat as many times as it takes to get the flavour you want. If the food you're seasoning is still raw (and can't be eaten raw), then just put in a small amount the first time you make it and keep track of how much table salt you needed to add.

Just remember, you can always add salt later, but a dish that's too salty is permanently ruined.

There's a bit of trickery going on in the comparison of vinegar (acetic acid) to spirits of salt (hydrochloric acid). Your 5% (0.83 molar) vinegar has a pH of about 2.5. You need much less of the stronger acid, HCl, to reach that same pH (2.5); in fact only 0.003 molar, a factor of 277 less. Since you taste the anion (acetate or chloride), not the proton (H+), it's no wonder that the vinegar is much more flavorful; there's a 277 fold difference in the concentration of the flavor agent. Pick a different acid, and you'll get a different tasting anion, and a different concentration needed to reach pH 2.5.

Response to comment on taste of anions:

Your linked Wikipedia article gives the impression that the taste reception system is fairly simple, and well understood. It is neither.

Here are a couple examples of reasonably current research on the taste of anions:

The Anion Paradox in Sodium Taste Reception

Anion size of sodium salts and simple taste reaction times.

Take a look at Wikipedia's article on taste receptors. you'll see that 'bitter' tastes are subclassified by 30 or more different receptors. Salty taste receptors (specific anion and cation) are still are poorly characterized

Research on humans is hard, so it'll probably be decades before the mechanisms of tasting are fully sorted out. Until then, consider sources like Wikipedia expositions of the current state of knowledge, rather than the final word.