This is reported by Stanford (CW-2995):
Lauren Cipriano, TA for F11-MS&E-193-01, reported that she tried to export the responses/scores from Homework Assignment #4 and ended up with an empty file. Karen let me know that Excel has a character limit of 32,767 for a cell. Our Short Answer/Essay question type has a 60,000 character limit. If just one student exceeds the character limit in Excel, which can be done with all the formatting tags that count towards the character count, the export will fail.
I think we need to adjust the Short Answer/Essay character limit to 32,000 so there will be no more conflicts with Excel.