It depends on your system of parsing. For example, code generated by a parser generator would be slightly more complex. A regular expression would also be slightly more complex.

I have written recursive descent parsers in the past, and if I remember correctly, the way I set things up, I had to handle leading list elements specially. It's possible that this was unnecessary and I was simply blinded to a simpler way of doing things because I was following the EBNF too strictly.

Edit: I noticed that we're not actually accounting for an empty list here. That makes things slightly more complex:

  comma-separated = [ element, *(",", element) ];

Your code would need to test if there is an element or a list terminator before processing the element.