I argued any character would be as "optimal" as any other character (although I prefer \t).
I tend to agree with this in theory but in real life, commas, tabs, and pipes are probably used most frequently.
You can get more efficiency out of the case where you are positive that your delimiter won't show up in your data. Otherwise, you really need at least two characters: the delimiter and a quoting (or escaping) character. The less either of those shows up in your data, the less processing you will have to do and the smaller your input will be. So, it is better to use a less frequently used character as the delimiter.
I disagree with you ex-supervisor's assertion that tab is "the standard." There simply is no standard.
-sauoq
"My two cents aren't worth a dime.";
