Opera has some problems in displaying the correct fonts.
In this case the „ and “ and following !

See below im text box.
Opera slants font, Firefox displays correct; see screenshot
Correct font display in Helvetica as screenshot below.

Text sample

Screenshot of problem with quotes and exclamation mark

Left: Opera 9.64; Right: Firefox 3

Correct display of Helvetica

Helvetica (Zoom 250%)

With Opera 10.51 the bug changed a little. But you can see, after zooming to 650%, that the wrong quotes are used. Opera 10.51 now uses the quotes from Arial instead of Arial and Helvetica.

See following image showing correct quotes of the fonts (differences between fonts marked yellow):