I tried it and it still says ANSI in the config. Here's from the Docker log on startup:
2017-03-14 13:12:10,523::INFO::[sabnzbdplus:1173] sabnzbdplus-1.2.1 (rev=d32cf57c7573ed43bcab40eb9b23a0853f1f7015) 2017-03-14 13:12:10,523::INFO::[sabnzbdplus:1174] Full executable path = /usr/bin/sabnzbdplus 2017-03-14 13:12:10,523::INFO::[sabnzbdplus:1186] Platform = posix 2017-03-14 13:12:10,524::INFO::[sabnzbdplus:1187] Python-version = 2.7.12 (default, Nov 19 2016, 06:48:10) [GCC 5.4.0 20160609] 2017-03-14 13:12:10,524::INFO::[sabnzbdplus:1188] Arguments = /usr/bin/sabnzbdplus --config-file /config --server 0.0.0.0:8080 2017-03-14 13:12:10,524::INFO::[sabnzbdplus:1190] Preferred encoding = ANSI_X3.4-1968 2017-03-14 13:12:10,524::INFO::[sabnzbdplus:1238] Read INI file /config/sabnzbd.ini
My startup says all commands completed successfully and it showed that the variable were passed.