Value not displaying in cart or on order receipt

I received an order in which the option was blank, but it was a required field. Upon further investigation, the customer claims they selected a certain option. I duplicated the problem myself, and sure enough, that option does not appear in my cart.
The option contains a comma: “Bob Smith, Conductor”
If I remove the comma, it appears properly.
Are there rules about what characters the options can contain? If so, where can I find them?
Thank you!