A Knapsack is a two strap bag worn on the back to carry supplies and equipment. Paragraph 675 of the Regulations
of the Army of the Confederate States, 1863, states: "When necessary, the orders specify the rations the men are to
carry in their haversacks. The field officers and Captains make inspections frequently during the march; at halts they
examine knapsacks, valieses and haversacks, and throw away all articles not authorized." These regulations make no
other mention of knapsacks.
Both were standard issue and required, however, either or both were frequently discarded depending on conditions.
The Echoes of Glory, Arms and Equipment and Atlas of the Civil War, three box set by Time-Life Books, 1991 shows a large
variety of them.
I have never heard of a "Comfort."