′ and ″ handled inconsistently

Dear Friends,

What to do when an author using TeX-like markup writes: $f'$
or $f''$?  This has certainly been discussed before.

Regardless of whether one uses  <mwhat><mi>f</mi><mo>&y;</mo></mwhat>
with  mwhat = (mrow  or  msup) and y = (prime or Prime),  the current
Firefox (1.5.0.9) is giving inconsistent results between &prime
and &Prime -- both in Linux and in WinXP.

I once thought it was a font anomaly, but now since I can
often, but not always, work around it with CSS, I'm inclined
to raise the question in what ways U-2032 and U-2033 are treated
differently in the code.

I believe, for example, in Linux that I'm looking at the Symbol font
and that 2032 and 2033 are glyphs with similar features.  (Is there
a way to verify this absolutely?)

For more, including links to pictures, see my comment today in
BugZilla 140439:
https://bugzilla.mozilla.org/show_bug.cgi?id=140439

Cheers.

                                    -- Bill