It seems a coke-sized can, requires only 13mg of this protein, compared to 200mg of aspartame.

If brands see that increasing the amount also increase sales without increasing the risk - they're likely to do that - which would numb the sweetness of anything else.

These are both very small amounts of a substance, relative to the size of a Coke can. I think if Coke wanted a sweeter formula, bumping up to 250-300mg of aspartame or using a blend of existing additives or something would not be a problem for them.

Given how sensitive consumers are to changes in its taste, I think the overriding concern for Coke would be not changing the flavor of the formula.

That's a good point, a good taste is often a concert and not a single-person band.

My point was more towards the end of the scale, it wouldn't be great if all food got sweetened to the limit - just to be able to get noticed at all.

If what you say is true, wouldn't we already be seeing incredibly sweet things being sold? I don't see why companies would hold back from producing very sweet products with high sugar content; they do so already.

I'm not sure anyone's clamoring for sweeter drinks. Non-diet drinks like Coke have an established recipe, and diet sodas approximate the same balance of flavors.

I think there is some level of hardwiring limiting the palatability of sweetness, at least in some people.

Anecdotally, even as a kid, I found Skittles to be unpleasantly sweet. To this day, I avoid most sweet soda drinks and seldom drink even those I can tolerate.

It is not discipline for me. It is not even taste. It is tolerance.