I am generally of the belief that some glyphs ought to remain upright even in italic fonts.
I have long used lists of such glyphs when working on italics—even reverse engineering a list at least once, looking at my own previous fonts.
Anybody else keep such a list they are interested in sharing or discussing?
My previous list as a text file (FontLab .enc format) is here: https://github.com/tphinney/science-gothic/blob/master/lib/encoding/upright-in-italic.enc
I am just about to update this for my current project, Science Gothic.