In many (or most) cases our users want to include cell formatting when reviewing Excel spreadsheets, because they become fairly unreadable with the formatting stripped out in the diff viewer.
This limitation means that either:
- The author has to format the spreadsheet nicely for printing and save as PDF or use print to review, which can be a lot of effort, particularly when there are multiple sheets.
- The reviewer has to download the file in Excel, and go back and forth between Excel and the collaborator web page to log comments. Because the Excel sheet is unformatted, and it's extra work to find the specific cell, the comments will tend to be logged in the 'general chat' area of the review.