In expert install mode ISPConfig offers /etc/proftpd.conf as default. The debian default path is /etc/proftpd/proftpd.conf Maybe this could be changed some time in ispc.
The perfect setup contains instructions to create a symlink for that. We can not change this in ispconfig at the moment as some of the older debian / ubuntu versions use the other path and the ispconfig installer uses the same code for all debian versions.
Ok, no problem. I did not know that. It's only a "nice to have" anyway, so no need to include it right away.