[latexrefman] Adjust font size section

[Karl Berry]

Indeed, the question of upright vs. italic differential d is a religious
(that is, like emacs vs. vi, arbitrary/meaningless, not literally
religious) one, going back (I believe) centuries. Barbara has a vague
plan to write a whole article about it.

Our job in latex2e.texi is not to promote one or the other, but describe
what *core* LaTeX commands do. I don't recall if there are any base
LaTeX commands relating to the differential, or if the amsmath package
(the only one possibly relevant) has any. If none, there is nothing to
say. I don't remember any, but I haven't explicitly searched for it,
We're not here to describe every package, either, only the most
fundamental ones, and even those only secondarily to core LaTeX.

My $0.02, even though I'm supposedly not involved :). -k