I did the classic "How are you?" with my native fruit attached on the first day (Sunday) and have yet to get anything back. I guess they took that out of the game, or made it take a lot longer. >_< Oh well.
Hrm, very strange. My replies came in 24 hours & each of my letters I'd sent included a shell. I suppose every town is different & your neighbors believe you're some kind of letter spammer! Hahahha, only kidding. Don't worry, they'll come around- the game is quite quarky. (=