Comment 90 for bug 913230

(In reply to comment #88)
> cc'ng derek, maybe he can help

Not sure how I can help other than to give my opinion which is I think we should immediately commit the patch from comment 40 on the grounds that it makes the GUI behave the same as the command line. No one complains about the command line using inappropriate media.
Nicolas expresses it well in comment 67

In response to tmb's concern about mgaupdate running while back ports is enabled I suggest that could be addressed by testing if any package to be installed comes from backports or 3rd party, and if so displaying a pop up on the lines of "You have backports/3rd party media enabled. You should disable this media if you do not want it to be used to satisfy updates."

Only a minority of users will be using back ports, and they are also likely to be more experienced users. If they choose to ignore the warning it is their problem.