I was also surprised to read this. One of the first things many
scientists would want to use superscripts for is to write e^{-x^2}.
Worse (or better?) I've had two users mail me (apparently
independently) wanting to know if foobar<sup><sup>3</sup></sup> was
"right" because they wanted to be sure that the footnote reference
would came out "nice and small, just like their wordprocessor does it"
(or words to that effect). I asked which browser they were using: I've
had no reply.
///Peter