I just searched for a few different mutations of the phrase "background transparency" in their bugzilla and didn't see any. I was expecting this to be a case of an end user not taking the time to see if their issue was already in the bug tracker, but if it's in there, it's hard to find. If there were really multiple bug reports (which I'm not saying there weren't) then bugzilla has a pretty bad search feature.
It's a pretty big problem when bug trackers are exposed to a group of non-technical users. Stackoverflow has a nice feature where it does a real time search of existing questions as you type yours in to prevent duplicates. I wish that was a considered a must-have feature of bug trackers.