Well, I think being promiscuous with "NA", "N/A", nan, etc. is a separate issue from a blank cell. A blank cell is literally missing. That should be filled with NA.
haha. You are right "NA" stands for "Not Applicable". That is not always how people/programs using it though. What are some alternatives that you would suggest? I am happy to learn.
I would suggest similar to what other people have suggested where you color the background of the cell red and then just display the literal content of the cell. I think it would be reasonable to have this configurable via command line arguments though, so if you like the "NA" that could also be a mode.
Perhaps it would make sense to have a "pretty" mode and a "literal" mode (which would also turn off the clever processing of numbers)?
