Originally Posted by mayday
Thru-hikers do not need a permit/reservation...but must give up their slot at the shelter if the shelter is full due to permit holders. Thus "If you have a reservation". Everyone else must have a permit (reservation). Thru-hikers do not need to self-register or have a permit.
Has something changed? Care to quote your source? According to GSMNP current regulations, everyone in the back country is required to have a permit. Thru hikers do not need to make reservations but are required to register before entering the park and marking their permit as "Thru Hiker". They are also required to stay in the shelters unless the shelter is full and then they are required to camp in the vicinity of the shelter. Again, unless something has changed these are the rules as I know them.