Hi Steve,
no doubt, the primary benchmark for every modeler should be himself and nothing else. It's simply a matter of settling your own claim.
Personally I find it exciting to search for references of a certain vehicle or type of and to build a kit according to that as good as I can.
So, as you would have liked the KV-II depicted with a turret's slogan, I think it's better left without.
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Not a big trouble.
I would be surprised, if a pic pops up, showing one. That hence we are talking about a type of vehicle of which less than 350 have been build and most abandonded or destroyed in the first days of war, when those slogans haven't been that popular (for prop-reasons - sometimes it seems as if most of the destroyed tanks lacked slogans and most of the intact, pictured by soviets, had
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). And most of them have been photographed by german soldiers! (http://mechcorps.rkka.ru/files/kv2/kv2.htm)
I think, trumpeter (and other kitmakers, too) added slogans to that kits to make them more attractive, that's it.
By for now
Volker