When I’ve installed Opera 10.63 on Debian (Lenny) I noticed some problems in rendering those characters even when typing text in textboxes on sites. I was playing with font settings in Opera, I have checked that Bitstream Vera Sans font is set anywhere possible, but still there was no success.
After some digging and playing with settings in Chrome, which was working good, I saw that it uses Arial and Times New Roman fonts which I did not have installed. It was strange, because when I clicked on the button to change the font it selected another one. But as I said in Chrome everything was ok, so I did not give that more attention.
Then after some more digging and looking for new fonts for debian I found out that there is msttcorefonts package available. This package contains basic fonts used in Windows. I don’t know why, but I have tried to install it. Then I went to Webpages tab in Opera Preferences and changed the fonts to be the same as in Chrome.
So as Normal font used Arial 16 and as Monospace font Courier New 13. Than I tried the pages that did not rendered good before and suddenly it worked like a charm!
I tried to change fonts in Opera back to default ones, but the problem did not appear again. I guess there is some hardcoded reference to those fonts in Opera, so installing msttcorefonts should be enough.