I know there have been a lot of ideas and discussion recently about duplicates and how to prevent them
my suggestion is less for giffgaff and more for the members with the power to mark duplicates (I dont know the exact list of who these people are? also is there a specific name for them? typing that out every time is slightly annoying )
When an idea is marked as a duplicate, if appropriate, the member who changes its status to duplicate should send a PM to the idea's author explaining about duplicates and encouraging searching. Hopefully new users would take notice and learn from this. This PM could just be a standard template, but I think a PM could be more informative and give more detail than just a one line comment on the idea thread saying 'duplicate' or 'please search in future'
I image that in some cases such a PM would not always be needed (e.g. senior/long standing gg member who should know better, or who did search but not using quite the right key terms so the previous idea did not come up). So its up to the judgement of the user who marks it as a duplicate whether or not to send the PM, but I think they are the people best placed to do this (as they are 'on the spot', as it were)
What do people think? For all I know, some members with the power to mark duplicates might do this already?