The byte for a capital I is the same as the start for an odd file format, slyk maybe? Excel has (or did if they finally fixed it) for years decided this was enough to assume the file (called .csv) cannot possibly be csv but must actually be slyk. It then parses it as such, and is shocked to find your slyk file is totally broken!
Yes but in practice CSV is defined by what Excel does.
As there is no standard to which Excel conforms as it predates standards and there would be an outcry if Excel started rejecting files that had worked for years.
There is a common misconception here. You can import CSV files into an excel sheet. You cannot open a CSV file with excel. That is a nonsense operation.
