> Exactly. "Use a delimiter that's not in the data" is not real serialisation, it's fingers-crossed-hope-for-the-best stuff.

It's not doing just this, you pick something that's likely not in the data, and then escape things properly. When writing strings you can write a double quote within double quotes with \", and if you mean to type the designated escape character you just write it twice, \\.

The only reason you go for something likely not in the data is to keep things short and readable, but it's not impossible to deal with.