Sure, sub/superscripts are most commonly used in math. Thus @math, as in @math{e=mc^2}. I never expected anything else to be used, certainly not clunky macros. This is why @math was created in the first place.
Is your proposal really just working around makeinfo not recognizing ^ and _ in math in the first place? It seems to me that might be implementable without too much trouble -- the parsing could maybe be treated like the accent commands, so that if the next thing is a non-lbrace single token, the braces aren't necessary. Seems to me that could only help, in any case, if it's doable. Patrice, wdyt? In HTML etc., the output is always <sup>...</sup> regardless of text or math mode, since nothing but TeX distinguishes. Having been drafting the documentation, I can say that it feels quite clean to say "use @sub/@sup for text, @math{^_...} for math". It's no problem to implement @sub/@sup being like ^ and _ in math mode and doing text in text mode, etc., but, I don't know, usage doesn't seem as clear. If I may dare to generalize a tiny bit -- in principle, I'd rather that we recognize TeX math in the first place than invent new Texinfo commands to do the same thing. karl