I'm running Opera in always in private mode (with switch -private)
Unfortunately, since the latest version 33 the extension icons are no longer shown in the private Windows although they are enabled for private mode in extension manager. They extension icons are hidden by default.
To get them back I have to go to extension manager and uncheck "Hide from toolbar" and then check it again for each individual extension. This solves the problem temporarily but for the current session only. After closing Opera and restarting it the icons are gone again.
Looks like the appropriate settings are not properly saved ??