I kind of did a work around. In the RSVP Options window, I changed the verbiage in the ‘Note Verbiage’ to say something like “Other notes”. I discovered that when you leave that field blank, it defaults to a system-defined message.
So to handle the food allergies issue, I created a custom question that asked “Please specified any food allergies”, and then the other note just says “Other Notes” and is a space where the guests can leave additional comments. Hope this helps.