When using an italic font (tested with lucida grande fontset,
variable-width), glyphs overwrite parts of previous glyphs. It looks
like single glyphs are shown on the screen with a white background
color, on top of the previous text. Upon redisplay, everything looks
good, which means that this only occurs after typing text as opposed
to pasting, or making it italic after typing.
The attached screenshot shows the effect: look for the letter 'h'.

I could not reproduce the problem with an X11 Emacs on GNU/Linux.
It does occur with a Carbon Emacs, though.
In GNU Emacs 22.0.50.4 (powerpc-apple-darwin8.2.0)
of 2005-07-19 on lucy - Aquamacs Distribution 0.9.5 beta-1 -
Aquamacs Distribution 0.9.5 beta-1
Distributor `Apple Computers', version 10.4.2
configured using `configure '--without-x' '--prefix=/usr/local''
Important settings:
value of $LC_ALL: nil
value of $LC_COLLATE: nil
value of $LC_CTYPE: nil
value of $LC_MESSAGES: nil
value of $LC_MONETARY: nil
value of $LC_NUMERIC: nil
value of $LC_TIME: nil
value of $LANG: nil
locale-coding-system: iso-latin-1
default-enable-multibyte-characters: t
Major mode: Outline
Minor modes in effect:
smart-frame-positioning-mode: t
longlines-mode: t
recentf-mode: t
osx-key-mode: t
mouse-wheel-mode: t
show-paren-mode: t
delete-selection-mode: t
pc-selection-mode: t
cua-mode: t
encoded-kbd-mode: t
tooltip-mode: t
auto-compression-mode: t
use-hard-newlines: t
menu-bar-mode: t
global-font-lock-mode: t
unify-8859-on-encoding-mode: t
utf-translate-cjk-mode: t
column-number-mode: t
line-number-mode: t
transient-mark-mode: t
next-error-follow-minor-mode: Fol
Recent input:
<return> M-o t h e SPC <backspace> <backspace> <backspace>
M-o i M-o i t h e SPC s h e e p SPC t h a t ' s SPC
r e d M-o i SPC a s SPC o p p o s e d SPC t o SPC <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <escape> o d a
s SPC o p p o s e d SPC t o SPC <escape> o i t h e
SPC r e d SPC s h e e p <menu-bar> <help-menu> <re
port-emacs-bug>
Recent messages:
Longlines Mode enabled in Text modes
Longlines Mode disabled in Text modes
Auto Fill disabled in Text modes
Auto Fill enabled in Text modes
Longlines Mode enabled in Text modes
Making completion list... [3 times]
Auto-saving...done
Auto-saving...done
Font-lock mode will override any faces you set in this buffer
Font-Lock mode disabled
_______________________________________________
Emacs-pretest-bug mailing list
[email protected]
http://lists.gnu.org/mailman/listinfo/emacs-pretest-bug