Tammy Wofsey, painter and maker of books, accompanied me and is the author of the above quote, referring specifically to a Chris Ware page of original art with heavy reworking.
(Examples of her work can be found online here and here by the way.)
Her great aphorism also applies to most of the art in the comics show since it was all made for reproduction and blue-pencil, white-out and overlays are common since the "real thing", so to speak, was the reproduction, not these originals now exhibited behind glass, but once carelessly piled in back rooms or summarily disposed of.
The physicality of the marked up originals just adds to their vitality (same as the Rouault prints at the MET and for much the same reason).
The reworked cover for MAD #1 and 2 Kurtzman shorts, '"Corpse on the Imjin" and "Three Dimensions" were standouts for me today. A lean, unglamorized war story and a wild parody of the 3-D glasses fad mixmastered with a critique of the comics form itself--each story 6 pages--a reminder that this master cartoonist was expansive in scope and economical in means.