I want some sane way of writing i^2 and R^4 so I get tolerably-looking expressions with superscripts in both TeX andDocBook/HTML.
Sure. First, with non-letter superscripts (numbers, +, etc.), you're fine with the present @sup inside math, regardless of whether @sub/@sup mean text inside math for TeX, because numbers are typeset by TeX in roman, not math italic, in any case. makeinfo presently outputs @math as <em>...</em>, which results in italic sub/superscripts inside @math (as well as everything else), regardless of their content. That's inconsistent with TeX, but I think it's expected and reasonable for HTML. Implementing ^_ in makeinfo would allow for better matching of input/output, i.e., allowing documents to use ^_ inside @math and get the expected output. I think that's desirable for its own sake, separate from any question of @sub and @sup. Anyway, it's alphabetic sub/superscripts where the question of whether @sub/@sup means "text" inside math makes a difference to TeX (nothing else). I'll await Patrice's comments before finalizing the TeX versions and documentation. I don't feel that strongly about it. karl