Just my opinion, but I doubt " John Q" public has much of an emotional investment in these characters to walk away from those examples thinking they are "fact". I seriously doubt "John Q" are as "confused" when looking at Ceasar Romero's Joker and then Dark Knight's version of the same.

Just like as "kids" we watched the Superfriends and if we walked in to a comic shop we didnt expect to see cardboard cut outs of the same characters.

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Sure you did, or why would you have been walking into that comic shop in the first place? You certainly would not have gone in thinking I wonder if the actual comics interpret these characters differently from how they are portrayed on the cartoon show?

Finding the characters portrayed differently, you would doubtless have adapted quickly, and perhaps even preferred the comicbook versions. Or been able to segregate them once you knew there were different versions. But to say you didn't expect them to be the same is disingenuous at best!

As to civilians and how they react to different versions, of course they are not going to be "confused". They accept whatever they are told, and each version writes over whatever they remember of the previous one. They're not likely to be comparing Heath Ledger to Cesar Romero in any case, unless they have long memories. The point of comparison, if any, would be Jack Nicholson, and I suspect it's no coincidence that Ledger's version has a scarred face, like Nicholson's. The latest movie was doing its own version of Nicholson's Joker, not the Joker from the comics.