The situation that comes up the most often that you need to consider is when someone embeds the same sort of file into itself, or chunks of the same sort of fil

The situation that comes up the most often that you need to consider is when someone embeds the same sort of file into itself, or chunks of the same sort of file into itself. If using the ASCII characters to delimit fields was common, you'd need to consider that over the course of some moderately interesting system's life time the odds of someone copying and pasting something from an encoded file into the spreadsheet application and picking up the ASCII control characters with it is basically 100%. And while we may be able to say with some confidence that nobody is going to embed a CSV file into a CSV file (and I say only some confidence, the world is weird and I'm sure someone will read this who has actually seen someone do this), there's other situations like HTML-in-HTML (for example, every HTML tutorial ever) that are guaranteed by their nature. It is still valid to disallow the ASCII control characters, one just has to make sure that it is done comprehensively, in all places users may input them. But that's not created by using ASCII control characters, that's a consequence of the "ban the control characters entirely" approach regardless of what the control characters are. It's neat when you can get away with it, but I generally prefer to define a robust encoding scheme instead. A minimal one like "replace backslash with double-backslash, replace control characters with backslashed characters" and "replace backslash sequences with their control characters, including backslash-backslash as a single backslash" can be inserted almost anywhere in just a few lines of string replace (or stream processing if you need the speed). The only tricky bit is you need to make sure you get the order correct or you corrupt data, and while I've done this enough to have it almost memorized now I do recall feeling like the correct order is backwards from what I naturally wanted the first few times. But it is simple and robust if you get it right.