Subscribers can add NOTES to their subscriptions, if you allow this, when they sign up. In Home / Settings / Option Settings / Subscriber Settings check the option 'Add Packing Notes to Subscriptions'. This allows members to indicate allergies, etc.
You can also allow members to add/edit specific Box Notes on a single delivery. This might be used to indicate to the farmer 'send more berries' or 'pack the largest tomatoes possible'. This should not be used for delivery instructions.