In the instance of "Infinity Crusade" I would say that errors like this happen most when editors don't do they job and writers are over-seeing characters from a line they don't work with. Calling Jean "Marvel Woman" and Madrox "Duplicate Man" are things that should have been easily resolved before going to print since neither had ever used those names in their 20+ years of existence in the books at that point. They were trying to push out this company-wide event and didn't likely make efforts to fact-check or proof-read.
I do enjoy Scaret Witch tho...