As I continued to slog through the KRV, I came across this passage in the Kemp Smith translation: "Appearances demand explanation only in so far as the conditions of their explanation are given in perception; but all that may ever be given in this way, when taken together in an absolute whole, is not itself a perception." This all sounds very Kantian, and to be honest it also strikes me as rather true and important.
However, there is one thing which can't help but make one worry. In a footnote, Kemp Smith indicates that the "not" in the passage above is not based on Kant's German text, but on the fact that the text makes no sense without it. Indeed, in context, the sentence without the "not" wouldn't make any sense (and Kemp Smith is not the first to have noticed this; he cites Mellin as the source of his reading of the passage), but it is hardly unusual for passages in Kant to be very hard to interpret.
I guess I think the "not" really does belong there, but I really, really wish Kant had had an editor. Or that he had put some tiny amount of effort into cleaning up his text himself.