[JadeNB]

> The most general solution is to have a "start superscript" and "end superscript" marker, with the ability to embed superscripts, but that still doesn't solve the isotope representation problem.

Couldn't one have something like a "start zero-width superscript" marker, so that the following subscript would not be offset?

[dragonwriter]

> Couldn't one have something like a "start zero-width superscript" marker, so that the following subscript would not be offset?

Well, the problem is that the subscript and superscript are both aligned with the following regular text, so you really need (for the isotope representation) a "start right-aligned zero-width superscript" marker, a "start right-aligned zero-width subscript" marker (though zero-width isn't exactly right, since they should have width, its just that only the wider of the super- and sub-script in a pair should be used in spacing the text) -- there might be other notation that also needs left-aligned versions of -- plus generic start/end superscript markers that have normal width flow, plus appropriate end markers.

[JadeNB]

It's not surprising that an offhand suggestion doesn't magically solve all problems, but I appreciate your taking the time carefully to explain what's missing. Thanks!