Importing order comments from Magento 1 to MyFullfillment is possible.

Comments are imported in MyFullfillment ONLY when the order is imported.
We will not import comments in MyFullfillment after the Order has been imported already.
1) Enable the Configuration >> Import orders comments => Yes
2) Enable the visible store front option when creating the order & comments in Magento1
3) Import the orders to MyFullfillment. You will find the imported orders with comments about the Sales >> Order.