I guess that \Cpp{} was introduced to avoid the hideous looking "++" with the PDF's font. There are plain "C++" that would look better if they were replaced with "\Cpp{}". check.sh should be enhanced to detect these. This may be obvious to pro LaTeX users, but pay attention to the index entries containing "C++". Some come from macro definitions like \defnx{\Cpp{} standard library}{library!C++ standard}, which should also replace the plain "C++" with "\Cpp{}" so that the index looks nice too.