$wgDebugToolbar = true; does not show the debug toolbar on Opera 12.16. In the console is a javascript error "Cannot convert 'this.data' to object"
It refers to the line 153 in mediawiki.debug.js:
paneTriggerBitDiv( 'console', 'Console', this.data.log.length );
this.data seems to be null here
Version: 1.22.0
Severity: normal