The latest claim over at NeoGAF is that Wii U digital content owned by the previous owner of a second-hand console can be downloaded again free of charge by the new owner.
A gamer on the forum reports that he was able to download Trine 2 and Nano Assault free of charge after buying a second-hand Wii U. This can only mean that the digital titles are tied to the console itself and not the Nintendo Network ID used to buy it in the first place.
So what do you do if you want to transfer your Nintendo ID and all related digital content from one Wii U console to another? Well you have to send it to Nintendo itself.
Usually digital content is tied with the account ID and not the console. It’s unknown as to whether this was a mistake on Nintendo’s part or if it was intentional. Hopefully the firm will respond to the new claim and we’ll know if a fix is needed.