Answer:
It means he is confident and comfortable at the convention, it is something he enjoys and has experience with.
The town follows a tradition that kills someone once a year. Everyone agrees that the tradition must be followed, simply because it's a tradition, that is until they themselves are chosen to die. The townspeople do not want to die, but they are unwilling to break from tradition.
"It had a perfectly round door like a porthole" (page 15)
"They used to go up like great lilies and snapdragons and laburnums of fire and hang in the twilight all evening" (page 5)
"Because their feet grow natural leathery soles and thick warm brown hair like the stuff on their heads" (page 2)
"My armor is like tenfold shields..." (page 226)
