I have a huge CSV file with lots of grades for a paper exam, and some of the e-mail addresses in my Excel spreadsheet are wrong (unreadable on the paper exams).
It's very frustrating to have to:
1) save as CSV
2) upload CSV
3) have moodle complain about the first e-mail address it can't find
4) fix the e-mail address
5) goto 1
It would be much better to have the gradebook print a complete list of all the mappings that failed, so I can fix these things all in one shot.